Add vehicle ramps

[demiurgeQuantified]

Add the ability to dig vehicle ramps.

As digging a ramp would take far more time and energy, the action should work differently from stairs:

• The player should use the dig cursor to mark an area for digging.
  • The area should be marked visually with something like construction tape or wooden pickets.
    • Whatever form it takes, this should not require any items, as 'you need tape to dig' is an arbitrary contrivance.
• Right clicking a marked area should offer an option to dig.
  • The digging should be completed in stages: each stage reveals one portion of the ramp. After each stage, the character is fatigued and sacks are filled with dirt like when other digging actions are completed.
    • The character should automatically start digging the first stage after marking the area.
    • After a stage is completed, if the character meets the requirements for the next stage (not fatigued, has enough sacks, etc) they should automatically start the next stage.
  • Cancelling the digging action should keep the progress from completed stages.
• Right clicking a marked area should also offer an option to 'fill in', which replaces any currently created ramp sections with dirt and unmarks the area for digging.
• There should be reasonable preventions from players constructing new things in the marked area. It will probably be hard/impossible to prevent weird interactions with mods, but it should at least take deliberate effort from the player to break things.

If timed action cheat is enabled, all stages should be completed instantly. A sandbox option for the entire digging to be completed in one action should probably also be provided.