Add interface definition for logger module
Add logger/module.c to CMakeLists.txt
Add stubs for logger module
Add implementation for ws_logger_new()
Added singleton cleanup function
Add basic implementation for ws_log()
Fix: Move logger type to source file
Fix: Interface/Impl. of ws_logger_new() to return status instead of logger object
Fix: Use early-return in ws_log()
Allow NULL as etc value
Reimplemented logger for less overhead
Merge pull request #56 from matthiasbeyer/add-logging

[WIP] Add logger module