Little Housecleaning

Cleaned up some messy preprocesser defines.
Fixed Unique Improvement Boost

The score boost from unique improvements is now applied after possible
overwriting of a tile's yield.
Religion Plot Terrain Scoring Considers Feature

The score of a belief based on the terrain of a plot is no longer added
to the total score if the plot has a feature that would override the
boost anyway (eg. forests with Dance of the Aurora).