Revert "Merge branch 'master' of https://github.com/Nightinggale/Medieval_Tech"

This reverts commit 70e24492f4547ef23a9e54a7e93ece0121dd8c30, reversing
changes made to 3cbfea28d6a38cf0466c4902515c65d535bf03a9.
Reapplied: New Building Attribute in XML Part 1: iCenterPlotBonus. This adds a bonus to alls goods produced in the center plot.