Add item priority: Ignore

Allow setting items (or groups) to be ignored - receiving said items will not produce any messages to output channels, regardless of other item settings. Respect existing settings chain (i.e. a group ignore will override its constituent item settings, but an item ignore will not override group settings).

Add a new priority value: Ignore. Continue incrementing received count for item (and its group, if any).

Use cases:

• LttP: picking up own dungeon items (map, compass, big key) w/o Keysanity
• SM64: along w/ thresholds, known number of Power Stars needed, then remainder are completely useless