Fixed tabs
Add in support for generated structures and map overlay

* fixed coordinate offset
* moved entities to overlay
* different entity types have different colors
* generated structure properties can be browsed by double clicking on the map
Fix whitespace
Entity properties work for horses again
separate entity and generated structure logic.

Also, performance enhancements
separate structures from entities in the menu.

Also, discriminate options by dimension
Switch around iterator types for compiler compatibility
Merge pull request #51 from thewierdnut/master

Entity/generated structure overlay, take #2