Framework updates

Mainly a change in the internals of GDAL – I decided to hide the included support libraries. Letting others link to the support libraries is a bit fragile, since they’re not guaranteed to stay there, or in the same form, and others who build their own GDAL framework (once it’s an option in the GDAL source) may not include them. This includes removing the Libraries symlink at the top level, unix/lib only has libgdal in it, and headers are only present for GDAL itself.