-Add: make it possible to pick your own blitter (-b <blitter>, -h for overview)
-Add: added a new optimized 8bpp blitter (default, caches sprites of all zoom-levels)
-Add: added a debug 8bpp blitter and a very slow normal 8bpp blitter
-Codechange: unified the blitter function so we have 1 function for all zoom-levels
-Codechange: make most of the label functions work with zoom-level instead of magic numbers and big switches per zoom-level
-Codechange: MakeXXXDirty() functions didn't take into account zoom-level, but just used the biggest possible value
-Codechange: simplified blitter functions to avoid code duplication
-Codechange: introduced ZOOM_LVL_DETAIL to show/remove details
-Codechange: changed << and >> operator with ZoomLevel to a simple wrapper (that in theory also allows zoom-in besides the current zoom-out)
-Fix r9845: missed some int -> ZoomLevel