Bugfixes & other changes (including ones to make the source buildable for now)

Changes made in commits include following minor bugfixes.
* NewTheater/structure image filename handling changed to support YR-specific theaters.
* Loading buildingz.shp no longer crashes with YR (has different file extension there).
* Z-buffering code no longer crashes with building images above certain height.
* Z-buffering code had a line removed that caused every building image to be rendered incomplete (unsure of the purpose of that line, unexpected side effects possible due to this change).
* Declaring custom palettes that do not exist on objects no longer causes a crash.
* A crash no longer happens when saving PNG render images (used to assume certain string contains a substring that differs between JPEG/PNG rendering).

Also following changes to add in extra functionality.
* Mod config now allows declaration of custom filenames for rules and art ini files. If multiple filenames are set, any files after first get merged with the first/primary file.
* Experimental change to support Ares NewTheater handling where any letter is OK as a first letter of the filename.
* Object (building, infantry etc) palettes no longer get any lighting effects applied on the color indices 240-254, which replicates the game behaviour with these colors.

Additionally following changes were made to CNCMaps.Objects.Westwood to allow one to build that project.
* Removed duplicate classes.
* Added necessary references to other projects.
* Commented out obviously incomplete code.