Adding kotoeri support (Japanese text on MacOS)

[vaicine]

This also fixes a little error when deleting text when there is no text, and a little tidying up.

Haven't tested for Chinese/Korean/other similar languages, but I believe it works the same.

[yairEO]

hey, thanks, but..I cannot merge such a pull request..
this is a big change just for one specific language, you've changed too much stuff..

[vaicine]

The stuff that is relevant to japanese/chinese/korean input isn't much change, and it's only used when japanese/chinese/korean is an input. Perhaps I should have done the tidying up part in separate commits so it's more obvious what is what.

I'll post a link in issue #5 to my fork so they can use this version if they still asian input support.

[yairEO]

I'm closing this. if any Asian wants this support, he can look it up in the issues sections, but for the benefits of most users, I do not want to bloat the file size. This project was intended only for English usage..