Add changeInstances command to VBSP

[TeamSpen210]

Add "changeinstance" command, swaps instances if conditions are met
This allows making most of the style-based modification

• check for conditions in load_entites
• can change based on:
  • quote pack
  • style option
  • Coop
  • isPreview
  • key name is "ifQuote", "ifStyleTrue", "ifStyleFalse", "ifMode", "ifPreview"
    • first 3 have value of target item, last 2 have value of true/false/1/0
  • perhaps "OpType" "OR" or "AND", decides if the conditions are read as an AND or OR op
  • implementation: store all unsatisfied in one list, copy contents to another when satisfied.

[TeamSpen210]

I'm changing this to merge with packing ability, instead it'll define a "conditions" list which when satisfied will allow changing the loaded config values during runtime. This adds the "inst_flag" condition (if the value is in an instance filename), and the "ifMat" condition (is the material used in the original VMF)?. It will be undefined what order conditions are run in, so they should not be chainable.

[TeamSpen210]

Done in commit f582242