[Expansion] Content Filtering Adjustments (#1910)

* Change default expansion values for ALL to -1 from 0

* Adjust content_filter_criteria

* Refactor content filtering logic

* Allow flag strings to also just be empty instead of null

* Formatting

* Editor oops

zone/CMakeLists.txt

@@ -459,6 +459,7 @@ SET(gm_commands
     gm_commands/refreshgroup.cpp
     gm_commands/reloadaa.cpp
     gm_commands/reloadallrules.cpp
+    gm_commands/reloadcontentflags.cpp
     gm_commands/reloademote.cpp
     gm_commands/reloadlevelmods.cpp
     gm_commands/reloadmerchants.cpp