Fix null error on resurrect mechanoid

Add new "custom item count" field for bills
Made "count from stockpile" work
Repositioned "count equipped" and "count tainted"

Quick patch to prevent error on bills that don't have a produced thingdef

Completely reimplement bill interface internally.
What does this mean for users? Less bugs, mostly, otherwise nothing yet. But this gives me much more power to change the menu.

Fix enumeration error when uninstalling bill becomes null, e.g. when workbench is uninstalled.

Add mechanitors, mechanitors bandwidth and mechanitors intake.

Add tainted and equipped searching + fix HP searching.
Add incompatibility with Better Workbench Management.

Change to new variable naming system. Current system is still supported for now, but will not receive updates and will be removed soon.

Fix null reference error when map is abandoned.

Add some more rules for special characters.