Make sure the user-manual.html output always ends up in $(OUT)

If you're doing a non-local build, it would get saved in the source
dir. Then qmake would complain that it couldn't find it in the target
dir.

Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Set the NSPrincipalClass in Info.plist

This is required to enable HiDPI support for the Retina displays. The
Info.plist that comes with Qt had this, but the one we supply with
Subsurface didn't.

Done-with: Jake Petroules <jake.petroules@petroules.com>
Signed-off-by: Thiago Macieira <thiago@macieira.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>