Feature/77 UIs look nice for all screen sizes and screen rotations

[NicolasVial]

Add :

• Tablet compatibility for all UIs
• Compatibility with screen rotations (for phone and tablet)
• Refactored CategoryEditing UI

Comment :

• I didn't touch MainActivity since we are always modifying it. Tell me if you want it to be cleaner and "tablet + rotation proof".

[Nitwix]

There is a crash in the learning presenter when there is no next picture in the dataset. I'll push a quick fix shortly