[harm_unit]: moved support function bool() to the start of the tag

This change is needed to have the function available for the whole tag.
[harm_unit]: renamed bool() function to toboolean()
[harm_unit]: moved the harmer advancement check inside the for cycle/valid check
[harm_unit]: added fire_event keys to wml_actions.unstore_unit tables

Fix for bug #20836
[harm_unit]: added animate keys to wml_actions.unstore_unit tables
[harm_unit]: removed two accidental plus signs that broke the tag
Fixed a missing frame in Troll Hero unit
Merge branch 'master' of github.com:wesnoth/wesnoth-old
Changelog entries for my previous commits