Config refacto

refactorisation, the goals were :
    * to avoid using any global variable
    * get rid of every occurences of 'libe'
    * cleanup how settings are passed and used
    * get rid of jdpicker (it is easy enough to hook any date picker if you want one)
    
Note that there is still a lot of TODOs in the code, and that this will make other pull requests hard to merge (some files got deleted, others got moved)