[FTR] Added new CommonObjectBase class
[FTR] Added new CommonObjectBase class

This class is for holding commonly used methods that are used by several classes.

It is inherited by the following classes:
    Category
    Conference
    Session
    Contribution
    Subcontribution
    Material
    Resource

I have only added one method, getRecursiveAllowedToAccessList(), which checks the
access control level, access list, and parent access list to get a full list of
all avatars/e-groups allowed to access the current object.

OmeGak/indico,DirkHoffmann/indico,DirkHoffmann/indico,pferreir/indico,pferreir/indico,mvidalgarcia/indico,indico/indico,OmeGak/indico,mic4ael/indico,DirkHoffmann/indico,OmeGak/indico,pferreir/indico,mvidalgarcia/indico,indico/indico,mic4ael/indico,mvidalgarcia/indico,ThiefMaster/indico,DirkHoffmann/indico,mic4ael/indico,ThiefMaster/indico,indico/indico,indico/indico,mvidalgarcia/indico,pferreir/indico,ThiefMaster/indico,OmeGak/indico,mic4ael/indico,ThiefMaster/indico