RainbruRPG's logger moved to OLD/ directory

Today's work (commits #821 and #822) is about code reorganization and the logger library.

Since I decided to switch to cmake and run integration tests, the multi-project layout was a mess.

Before the switch, every single binary/library has its own sub-directory and build system. The result is a bunch of different autotools scritps, each whith its own dependencies.
After the switch, all the components of the project will be build with only one command.

The logger/ directory finally moved to OLD/ and the code now lives in src/logger/. The meta/ directory also moved due to a complete re-implementation in the future.

Next libraries to be moved are services and network then the two binaries client and server will be placed in the same src/ tree.