Merge pull request #731 from RotaruDan/editionView2

EditionView improvements.
Minor changes.
Some improvements in PrefabsPanels widgets
Added add text functionallity.
Now mockup use a MockupEngine that extends Engine for not use EditableLabel
Added navigation panel.
Added DeparturePanel.
Minor fixes and improvements.
Merge pull request #732 from gorco/ExitsPanel

Exits and Navigation panels
WIP painting, elements context, fixes, edition, threshold, saving, image colliders...