Building a RailRoad increases the trade produced on a tile by 50 % this
is applied after other tile improvements but before goverment and city
advancements are accounted for. the movement points required for a move
between two tiles with railroads are 8 % (12 % for transversal moves) of
the unit models movement points (in cEvo sometimes called speed).
CevoIndexedObject represent the cevo objects that are normally adressed by
an index but the identity is maintained by the ID and additionally the
objects decease without notice (which makes is necessary to cleanup).
The form of government affects among others: formula for corruption, the
amount of food required to support a settler, how many military units are
support free.
The cost multiplier af a model changes to this amount when the prerequisite is
researched, except the prerequisite is a future advance, then cost
multiplier has to be added