Make build() and recycle() more robust

[hexagonrecursion]

Main idea:

• Cancelling a partially complete build() should result in a usable titanium cube
• Cancelling a partially complete recycle() should result in a usable wreck

Full change description:

• Fix #1756
• Fix #1757
• Fix #1413
• Fix #1428
• Fix #1025
• Adds a partial workaround for #1755 - prevents buildings, titanium cube and wrecks from getting stuck in an unusable state if the game is saved while a build() or recycle() task is in progress
• Some code cleanup/refactor