Cleanup the repo

[mclegrand]

• update dependencies
• remove untranslated brazilian files
• update all source code references to github
• use the github "releases" scheme
• remove zipfiles from repo
• update debian packaging
• prepare for a 0.20 release

I have changed the appdata id to com.github.key-mon but since the original copyright is Google's it would be also acceptable to put com.google.key-mon, at your discretion. In that case it would be more conformant to put com.google.keymon because dashes are discouraged in ids. (I have left it for github because there is a different tool called keymon hosted on github)

[mclegrand]

Note : I have not yet tested building a deb file from this, merely updated and adapted the existing.

[mclegrand]

(rebased)