[WIP] Feature/move scripts folder to assets

[adriengivry]

Description

• Removed the requirement to have all the scripts inside of the Scripts/ folder
• Added folder support for scripts paths
• Implemented a migration tool to automatically move scripts from Scripts/ to Assets/Scripts/, and update all scenes to use the new path

Related Issues

Fixes #385

To-Do

• Bug after exiting play mode: scripts become invalid
• Fix rename/move bug
• Get rid of projectScriptsPath
• Prevent same script from being added multiple times
• Base the m_scriptName on the lua table name instead of the m_scriptPath.stem()
• TScript should expose a GetTypeName() function
• Remove the notion of "Behaviour" from the TScriptEngine. The only thing TScriptEngine should do, is manage the context, create scripts from a path, register/unregister a script to the context, and provide a way to call a function (script, funcName, params)

Screenshots

When loading a project that uses the old Scripts/ folder

Migration tool output (moving scripts from Scripts/ to Assets/Scripts/)

Asset Browser with no more Scripts/ folder at the root, but one inside of Assets/