Better control of capabilities for sharing elements and configuring a tracker instance

Usually, a teacher wants to setup the layout of a tracker. It is worthly usefull to who creates the tracker instance to do this. Unfortunately, elements administration has been relegated to a global administrator, as he had opportunity to share elements in the whole platform scope.

The improvement adds new capabilities to dissociate the ability to equip a tracker with local elements (which can be given to teachers) and the possibility to tag them as shared.

A new capability will also allow a separate control of the network settings, that might NOT be given at a teacher level.