Levellump

[Alienmario]

This PR cleans up the levellump subsystem, adding comments, logs, optimizations and some breaking changes and fixing scarce bugs.

• Separation of entity property modification actions: add, set, replace
  • Add will no longer check for duplicate properties
  • Set will update or create an entity property if missing, never adding duplicates (preserved behavior)
  • Replace will only update existing properties
• Entity property deletion (entity->modify->delete)
  • Added value matching for non-empty values
  • To keep matching properties for deletion by keys only, the value has to stay blank ""
• This distinction is done primarily to enhance convertibility between Stripper:source scripts

This shall remain open until all edt scripts are corrected.

[ampreeT]

Looks good to me! Good job on adding docs where it was missing. We're going to have to test the campaign just to make sure nothing broke.