Create Asset Dock

[TokisanGames]

Fixes #132

• Renames Texture dock to Asset dock
• Makes it a real dock that can be moved around or pulled into a separate window
• Converts it to a scene for better editability
• Fixes crashes in Terrain3DEditor
• Toggles between side dock and lower editor
• Hides dock when Terrain3D not selected
• Can pin dock to prevent above when used as a floating dock
• Asset texture scale limits or slider
• Panel retains position when switching scenes w/ two Terrain3Ds. Updates to material list of selected terrain3D.

[Saul2022]

Tested it a bit and it look´s pretty good already the dock colocation seem´s to work well, except when putting in to the bottom one. While it works and it add it to the bottom docks it too big and ca´t be dissable unless you select other node other than terrain.

It seem´s it may be a screen size issue, though this is the default sethings, nothing was changed.

[TokisanGames]

Wait at least until it is not a Draft PR before picking it apart.
The bottom editor can be closed, just click the blue Terrain3D in the bottom bar, same as any bottom editor.