Improvements to TypeTree
Type system IR first pass completed
Moved types work in IR to a sub-package
Renamed CompileLog to MasoLangLog, updated all references
Initial addition of MasoTypeTreeBuilder and minor related changes to MasoLangUtiliites and Rectangle.maso. Also includes significant additions to Type and TypeTree. Related to issue #12
Merge branch 'ir' into develop. Note that work on ir is not yet complete (though is stable). This merge is being done to simplify the forthcoming migration to maven.