Reimplemented functionality for handling Kernel modules loaded on boot

- /etc/sysconfig/kernel:MODULES_LOADED_ON_BOOT has been moved
  to /etc/modules-load.d/*.conf files
- See also bnc#838185
Other than *.conf files are ignored
Added missing Makefile
CONSTANT-ized to cleanup the API

- some variables were accessible via API just for testing
  but constants can be also stubbed
Updated according to comments
Enhanced tests
Do not rewrite config file if configuration is not changed
API Cleanup

- Another method worth making private
Added changes file entry + new version
Added 'grep' into BuildRequires

- Needed for Kernel test
Adapted old test for Kernel library

- Testing of modules have been moved to RSpec-based test
A bit simplified test
Merge pull request #131 from kobliha/kernel_modules

RFC: Reimplemented functionality for handling Kernel modules loaded on boot