Move to CMake

[dmiklic]

Move the project from qmake to CMake. This will enable a cleaner project structure and we will be able to remove autogenerated files (.cc and .h files autogenerated from .proto files) from the git repo.

Warning: as a consequence of moving to CMake, we'll have to do a major overhaul of the Ubuntu packaging scripts, which is definitely going to be nontrivial.

[stribor14]

Autogenerated files are excluded from git repo, TravisCI initializes submodule and generates them himself during check