Added 'webm' conversion support

Added menu bar, added help dialog, added about dialog, added "Select Input Directory", "Select Input File" and "Select Output Directory" dialogs

Fixed delete files on export checkbox not doing anything

Merge branch 'master' of https://github.com/sonic2kk/Pyverter

Fixed incorrect spelling of AVCONV

Added Build Instructions to README.md

Rename LICENCE to LICENSE

Rename LICENCE. to LICENCE

Added LICENSE

Update README.md

Added README.md

Initial Commit