font collection class missing from Mac framework
Added unit test for #377
Changed _loadAvailableFontsIntoOverrideTable

instead of just having fonts overrule a previous override the strategy is now:

- add overrides with font descriptors sorted alphabetically first by family then by name
- if no override for combination of family, bold, italic traits exist, add it
- if one exists, replace it if the font name is shorter.

This prefers e.g. Helvetica-Oblique over Helvetica-LightOblique even though the -Light comes alphabetically before the font.

fixes #377
fixed Mac framework

- needed the -ObjC linker flag to include category methods from DTFoundation in itself
- removed superfluous static lib linking in MacUnitTest, since these methods are all bundled in the Mac Framework