Ammo & Fixes in 0.0.12

As I try to wrap up Demo 1 of 3, release version 0.0.12 brings many small improvements to damage behavior and adds:

• A short description dialog to the mission start.
• New item drops: currencies (and ammo). Both behave the same way and can be picked up even when your tow hook is carrying its max capacity. The first currency type, Scrap Parts, can even be used to refill your coilgun primaries.
• NPC components should be easier to kill. They now spawn using the same build system as the player, so I can perform damage tracking much more accurately than before.
• Extended the mission timer.
• Made golden Thief traders worse at their job. This is mostly an accident until I finish re-writing their mental code.
• Removed several menu options that won’t be implemented until version v0.2.x or v0.3.x.