Added file encoding support

Hey there

I've redone the file encoding support and tested it several times. Its now using the autodetection based on chardet.

### How does it work:
#### New Ini Setting:
fallbackEncoding (if the autodetection fails, this setting is used)
#### New Option:
editor.encoding (Overrides the autodetection functionality. Useful when you manually want to open files in specific encodings)
Okay i checked it in tge docs:
DefaultEncoding = which encoding shouldbe used for new files (this would be a great addition, since slap currently only creates files in utf8
FallbackEncoding = which encoding should be used if autodetection failed