Add quick converts for length units

[mvysny]

Currently Aedict is able to convert Japanese imperial years e.g. 平成1 or 明治一 or 平成1年 or 明治二年 to Gregorian date.

Having a converter for imperial length units would be handy: http://www.sljfaq.org/cgi/junit_length.html

[mvysny]

Even better, use this table: http://www.sljfaq.org/afaq/units.html#length_units
Just convert to mm/cm/dm/m, whatever's most appropriate. E.g. searching for 10尺 would show up as 303cm

[mvysny]

Beware that some of the units overlap, e.g. 分 is used both for length and for weight.

[mvysny]

Implemented in Aedict 3.39.33