fixed letters_from_lexington and narrowed map
updated pirates_and_emperors
Moved start location, added many trees.
updated pirates & emperors - no TEMPERAT trees
All trees are from the original C&C Desert tileset. Made a few tiny
changes to layout as a result.

The dense tree/cactus/rock areas near the bases have been thinned out
slightly.
Merge pull request #5367 from psydev/mapfix

Updated 2 of psydev's recent TD maps -- minor fixes
Added in the ability to put prereqs on support powers.