Commented out test case that loads tiles for Oregon.
Removed unused imports
Added Cache Interface
added cache object to all applicable tile set constructors
Moved creation of MegaTiles to static ImageTileMerger class.
create but ignore test output directory
Serialization of Tiles.
Test for serialization of tiles.
finished implementing sqlite cache using cache inteface. something is wrong, we are getting bogus tiles that dont line up right.