Dependencies Interface to visualize, modify, create and remove single dependencies

First version of the dependencies interface that allows schedule managers to visualize dependencies in a graph based interface, as well as rapidly creating and deleting dependencies, creating group of courses to smartly generate simple dependencies and dynamically check graph errors for managers to correct them.

The current version actually lacks few things, to be implemented later:

• A translation of the interface
• A second part allowing the creation of global dependencies as well as their visualization in the main interface
• The smart reloading of graphs only when necessary, not each time the course selection changes
• Fixing the lazy scroller when dependencies are displayed

Ref #86 (closed)