* Remove unused UNICODE(n) macro, update docs
* Add note about max length of unicode_map to docs
* QK_UNICODE_MAP → QK_UNICODEMAP
* Refactor process_unicode_map
* process_unicode_map → process_unicodemap
This is done for consistency: UNICODEMAP is the method (hence UNICODEMAP_ENABLE, process_unicodemap), whereas unicode_map is the mapping table itself.
* Update references and ordering in docs/understanding_qmk
* Add additional note to docs/understanding_qmk
* &unicode_map[index] → unicode_map + index
This avoids the issue of the compiler sometimes complaining about the array index being out of range
* Update docs/getting_started_make_guide
* Update method sections in docs/feature_unicode