Use OBS for building the packages

[marmistrz]

Using OBS has several benefits:

• new users don't have to compile swiften (assuming it's packaged)
• we can build for multiple archs (aarch64 soon, armv8el for the phones, i486 for the tablet)
• more strict dependency handling

The current WIP can be found here: https://build.merproject.org/project/show/home:marmistrz:swiften

Tasks

• Build newer boost
• Build swiften against new boost
• Build shmoose against those - partially done, linking fails
  • Make sure it compiles
  • Make sure it links
• Move boost to a different location so that it can be installed parallel to the system-wide (we can't simply replace it, since it's a revdep of libzypp)
• Modify the swiften packaging to use the moved boost
• Modify the shmoose packaging/source to use the moved boost

For OpenRepos we can (and should) ship the library as a separate package, if we want to target harbour, we can copy the libs for the harbour target. I