#138 Merge Action

Currently Xconq allows for units to increase the size
of advanced units under a certain condition. The
condition is that the unit must be able to create the
advanced unit and the unit must be an occupant of the
advanced unit. If these criteria are met, then
performing a create on the advanced unit results in the
size of the advanced unit being increased and the
creating unit to disappear.

One can envision this feature being expanded into a
separate action, a 'merge' action. Some possible
improvements over the existing functionality would be
'merge-range' and 'size-per-merged'.

'merge-range' could then allow one neighboring city to
swallow another, for example. The default would be -1,
which would make things behave as they do now.

'size-per-merged', if set to -1, would add the size of
the merging in unit to the unit being merged into. If
the merging in unit had no size, it would be treated as
a 0 size increase. If the 'size-per-merged' was 0, then
the merging in unit would be swallowed without any size
increase occuring. The default would be 1, like the way
things behave now. Numbers >0 would cause that much
size to be gained by the unit being merged into.