Fixed ja.jskakasi.j2h.J2H.isCletter

* Added libs.pyhelpers.PY_CONTAINS helper
* Fixed ja.jskakasi.j2h.J2H.isCletter
* Removed unneccessary double check of canConvert in
  ja.jskakasi.j2a.J2a.convert
* Improved Japanese test
Huge refactor

* Most importantly, Unihandecoder is now unihandecode.Unihan
* Namespaced everything (besides Klass, which is 3rd party) under
  unihandecode.
* As a resulting of the namespacing, everything was renamed. General
  rule is that language stuff is under unihandecode.<lang>, which has a
  Decoder and CODEPOINTS property (usually). Japanese also defines a
  whole bunch of stuff under unihandecode.ja.jskakasi(.data).
* Namespacing is done using unihandecode.helpers.module.
* Renamed pycompat to (unihandecode.helpers, renamed functons in
  pycompat to something more neutral.
* Added missing semicolons.
* Added tests for mixed ASCII-Unihan/Diacritic input.
changed the namespace of the JA codepoints to be the same as the other
decoders