Add Proxy course class to use it when no course selected (for example, when no courses downloaded or no active course)
Enhance player layout.
Add activity hierarchy.
Check left and right drawer - they works
Rework player activity with left and right side drawers.
Rename OpertingSystemFragment to PlayerFragment
Do refactor some layout files.
Added course adapter.
Added track adapter. Start modifying model in order to play course
Enhanced model and courseDAO to communicate together
File system is partially done.
The transformation model in the JSON file - done, but not tested 100%.
Move down methods parseModelJSONFile(), getModelJSONFileContent(), saveModelJSONFile(), convertModelToJSONString() and add comment about it.