#3 kanji filter preferences

[Horst Dehmer]

When searching or looking up kanji characters an
implicit filter should limit the resulting characters
to the more commonly
used characters. No need to always search thru all
12700+ characters.

Use grade level to classify characters:
- Grade 1 thru 6 (jôyô): 1006 chars
- Grade 8 (jôyô, general use): 939 chars
- Grade 9 (jinmeiyô): 287 chars
- undef. (others): 10505 chars