Remove RTS

[dashodanger]

This removes code related to parsing and executing Radius Trigger Scripts. In doing so, there are also the following side effects:

• MUSINFO music changer thing types have been removed (this is not necessary for custom content)
• Inventory item usage will decrement inventory counts but otherwise do nothing (all inventory items were named RTS scripts)
• Select maps from Freedoom and Blasphemer will not work as intended (mostly monster-death-related scripts like MAP07, E1M8, etc)
• Paths cannot be set for monsters (this does not affect bot pathing)