Add autotiled roads

[artism90]

Ported autotiling algorithm from the original UH and added road building mechanics. The unchecked tasks are meant to be done in a succeeding PR, so that the base functionality is already in place.

To check out tiling, open PlayerCamera node and set the root node's default_interaction_context to the TileContext sub node inside PlayerCamera. Also follow the note in the TileContext script in _ready. Later on, the context should be interchangeable through to the UI by utilizing PlayerCamera's switch_context method.

Requirements:

Two tiling modes:

• [x] Click and release to draw planned line from point of activation. Click again to place it effectively. (slow method)
• [ ] Click and hold to draw a planned line up to two cells minimum. Release to place it effectively. (fast method)

Abortion:

• [x] Cancel tiling in any mode immediately by the cancel action (right click by default).

Visuals:

• [x] Indicate valid lines (green).
• [ ] Indicate invalid lines (red).

Additional remarks (issues):

• Currently, the trail won't be built correctly along the terrain when the cursor is moved too fast. To resolve it, all GridMap tiles passed by the cursor should be registered (as a path in an array) and an appropriate A* calculated road built along of them.
• The trail should remain the axis it is drawn on for a certain extent to allow for straight lines to be drawn simpler (see FIFE UH for reference code).

Added Utils/GridMapCreatePathModes.gd which can be used on tile scenes (i.e. TrailMeshes, GravelPathMeshes, StonePathMeshes) to add differently colored tiles (green/red for valid/invalid cells).

[sairam4123]

Is this being worked on? Can I possibly help on this?

[LinuxDonald]

@sairam4123 @artism90 wanted to finish this pr. But at the moment he don't have the time for it. But you can start to work on some different if you like?