Removed references to x-attributes from classes other than XFSresource and lock_provider
Now also BeeHub_XFSResource doesn't rely on extended attributes anymore
Moved all properties to MongoDB instead of extended attributes
Eerste opzet om principals ook naar noSQL over te zetten
Moved all user data to MongoDB.

Almost every code concerning that is also updated, except for the notifications in
BeeHub::notifications() and some stuff in beehub_group(s) and beehub_sponsor(s)
as these need to be updated completely anyway.
All sponsors are now moved to MongoDB.
Again: notifications are still an exception
And now all groups are moved to MongoDB too
Fixed a bug in the import script from the mySQL database to MongoDB
Mainly changed mongoDB structure
Notifications are now made based on MongoDB too
Moved ETags to mongoDB
Replace a mySQL call to create an UUID, by a php function doing the same
Fixed a small bug in the lock provider
BeeHub_Registry now also uses mongoDB instead of mySQL

This was the last piece of mySQL that was in BeeHub!
Squashed two bugs. Most importantly, one where I forgot to delete the mongo document when deleting a file.
Dots are now replaced in property names stored in mongoDB.

Dots are not allowed in document field names, so they are replaced. Also did some fixes to the conversion scripts.
Changed several properties to just store the variable part

Properties like default_sponsor (of a user) and owner (of a file) stored complete paths
to the principals. But as all principals of a certain type are always stored in the same
location and each property can only accept principals of one type, it is shorter to just
store the name instead of the full path.

Example:
DAV: owner = /system/home/niek
now becomes:
DAV: owner = niek
as an owner can only be a user (in BeeHub)
Fixed a bug which made the last (shallow) read lock simply overwrite the previous one (instead of adding an extra lock)
Merge branch 'master' into nosql
Merge remote branch 'origin/master' into nosql

Conflicts:
	src/beehub_group.php
	src/beehub_sponsor.php
	views/beehub_user.php