FR: Shift-JIS support

[shyperson0]

Pretty much title, a lot of coleagues use Shift-JIS instead of Unicode, I'd like to keep all my work within ecode instead of having to use a different editor for Shift-JIS files.

[SpartanJ]

This commit adds Shift-JIS support. Feature should be ready but I'll test it a little bit more, since he heuristics to determine if a file is encoded with Shift-JIS are quite tricky.