Added adding/sorting kanji by JLPT grade. A few other minor changes.
Kanji List Editor:
* Add/Sort "By JLPT Grade" added.
* Removed Sort "By Both" (automated frequency-followed-by-grade sort).
* Reordered buttons slightly.
* "Grade" is now more fully specified as "Jouyou Grade", to prevent possible
ambiguitity between it and JLPT levels.
KanjiList:
* Fixed a bug in the AddByGrade function dealing with non-Jouyou kanji.
The code is now more clear and handles adding non-Jouyou kanji properly.
Version: increased to 1.2.2