.gitignore fix & Improbments

Hi, sorry to bother you again.

On linux when the gitignore start with a / it doesen't look into the current directory so it doesen't work . Without a / it works fine on Linux & Windows. It doesn't work on my server at least. 

Secondly I changed the way you ignore the config directory to ignore everything except config-example.ini. This way it is easier not to add by mistake config files created by some plugins

Lastly to develop we found it easier to continue to use the old installation where we use git(easy branch switching) and we put plugins in the ManiaLivePlugins directory as the "old days". Not to add them to the git by mistake I added that directory to the ignore list as well.