config: Generalize infrastructure build materials storage

[empserver] / tests / empdump / xundump-errors / ftr-mal2

config infrastructure
name             l_b h_b bmob cost enab
"road network"   200 200  100  200    1
"rail network"   100 100  100  100    1
"defense factor" 100 100  100  100    0
/con
# malformed table footer