`NPCTag`: modernize, `can_navigate_to` tag (#2811)
* NPCTag modernization & NPCTag.can_navigate_to tag
* miscellaneous changes
* extra space
* plain-text arguments
* minor changes
* minor changes
* minor changes
* reverted a couple changes
* minor change
* revert empty `set_nickname` mechanism and minor changes
(
commit: 6aa77dd)
