.gitignore: ingore bundles and bundle directories that are mapped from other source trees

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
AppKit: added a link to the system Foundation framework so that we can build the AppKit mixed bundle (using system Foundation headers but this AppKit)

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
AppKit: fixed build on Xcode 6.1 (almost) so that we are no longer mixing things with System Frameworks (unless needed)

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>