(info, html): Implement.

(all): Depend on info.

Flatten info directory.  This undoes the move to one subdirectory per
chapter, which was done during Empire 2.  The structure doesn't buy us
much, as the info name space is flat, and it complicates makefiles.

Overhaul info.pl:
- It now wants to run in the root of the build tree.
- Information on source files and subjects is now stored in makefiles,
  thus info.pl no longer picks up random junk from the file system.
- Clean up Perl anachronisms, in particular use subroutine arguments and
  results rather than global variables where convenient.
- Change format of diagnostics to the common format used by GNU tools,
  so that Emacs and the like can parse it.
- Catch missing .SA.
- When creating a new subject file, cowardly refuse to overwrite an
  existing file.
- Subject files contain topics sorted by chapter, then by name.  The
  order of chapters used to depend on how Perl sorts hash keys.  Fix
  it.

info/Trade-ships.t

@@ -0,0 +1,92 @@
+.TH Concept "Trade ships"
+.NA Trade-ships "How to use trade ships"
+.LV Basic
+Trade ships are special ships, with a different function than most Empire
+ships. They are in the game only if the TRADESHIPS option is enabled.
+.s1
+Trade ships simulate internal or external trade. In the real world, countries
+make goods that they can make cheaply, ship them somewhere they're expensive,
+and sell them, making a profit.
+.s1
+In the empire version, you make a trade ship, using lots of cm's, and costing
+$2500. You then sail it to a harbor somewhere and scuttle it. You then receive
+money, with a varying rate of return.
+.s1
+The trade ship MUST be scuttled in a harbor that is at least 2% efficient to
+make money. (In other sectors,
+it sinks quietly, like most ships) You may scuttle it in either a harbor you
+own, or the harbor of an ally. Pirates who capture a trade ship may also gain
+money from it, just as if they were the lawful owner (although the news knows
+the difference)
+.s1
+The return rate is based on the straight-line map distance from the harbor
+where the trade ship was built to the harbor where it is scuttled.
+.s1
+You have to sail it at least 8 sectors to get any money at all. At less than
+8 sectors, you get nothing, not even your $1750 back. Nothing, nada, zilch,
+zip, nothing. Once you make a trade-ship, you're pretty much committed to
+sailing it at least 8 sectors...
+
+Currently, the return rates are:
+
+.NF
+		Distance sailed		Return rate
+		0-7			NO MONEY
+		8-13			2.5% * distance
+		14-24			3.5% * distance
+		25+			5.0% * distance
+.FI
+.s1
+For example, if you sail the ship 10 sectors from the harbor where it was
+built and scuttle it in a harbor there, you would get 125% of the money you
+paid for it, or $2188. If you sailed it 15 sectors to a harbor and scuttled it,
+you would get 153%, or $2678. 
+.s1
+Use the \*Qpayoff\*U command to see how much the trade ship would pay
+were it scuttled in a harbour at its present location.
+.s1
+If you scuttle a trade ship in the harbor you do not own, you get a 20% bonus
+(applied after the value is multiplied by the return rate above), AND the
+person owning the harbor gets 10% of the cash you make as a bonus (the amount
+before the +20% bonus is applied)
+You still get the full amount, but he makes money as well.
+(Peaceful trade enriches BOTH countries more than trading only internally).
+For the devious, no, being allied with yourself does not mean you get +20% when
+scuttling in your own harbors.
+.s1
+For example, using the #'s from above, if you sailed 15 sectors, and scuttled
+in an allied harbor, you'd get $2188 * 1.2 = $2.6K, and your ally would get
+$2188/10 = $218.
+.s1
+CASH GAINED IS ALSO MULTIPLIED BY THE EFFICIENCY OF THE TRADE SHIP.
+So, if you get shot down to 21%, don't expect to get the full amount...
+.s1
+If you capture a trade ship, you are free to scuttle it in any harbor you can
+get it into, receiving full cash calculated normally.
+.s1
+The cash return is multiplied by the efficiency of the ship, so less efficient
+ships produce less money.
+.s1
+Captured trade ships may be scuttled as if they were yours (although you will
+get some bad publicity in the news) Payoff is still based on the distance from
+the harbor where the trade ship was built, not the sector in which it was
+captured.
+.s1
+You can also use the "order" command to set up automated trading routes with
+trade ships and have them navigate and automatically scuttle themselves when
+they reach their destination.  See "info order" for more information on this,
+but basically you can do things like this:
+.NF
+    Step 1) Make a harbor
+    Step 2) Get cms distributed/delivered to your harbor each update.
+    Step 3) Find a destination harbor to sail to
+    Step 4) build tradeships in the harbor each update
+    Step 5) load civs and food on the trade ships each update.
+    Step 6) order the trade ships to sail and autoscuttle in the dest harbor.
+.FI
+.s1
+You can then just repeat steps 4, 5, and 6 each update, and never worry
+about your trade ships again.  Unless someone starts intercepting them,
+that is...
+.s1
+.SA "payoff, order, Ship-types, scuttle, Ships"