Add abstract network classes
Merge branch 'develop' into feature/network
Edit opcodes_generator.py so it may now compile.
Implement serialization
Merge branch 'feature/network' of github.com:Ponyca/ponyca into feature/network

Conflicts:
	common/net/network.h
Fix previous merge.
Fix name of (un)serializeXXX().
Define coordinates, position, direction as Serializables.
Add UTF8CPP library to CMakeLists
Embed library utfcpp (cannot be found in most distributions' repositories).
Remove unused CMake module.
Add basic test case of serialization.
.travis.yml: Run tests.
.travis.yml: Add missing dependency.
.travis.yml: Add PPA to install cxxtest.
Fix previous commit.
Fix previous commit (#2).
Implement string/list serialization
Move (un)serializeList implementation to .cpp file.
Fix tests.