The locale can now be configured in settings and is stored in
Vuex. The changes are applied immidiately after selection. The list of
languages is taken from the messages file, which contains all the
available locales (and a new value, `interfaceLanguage`, to control
the translation of this option in the options menu)

Closes #36

Alternative autocompletion is in the works and this one has injection problems.

Pako was very slow in Chromium.

We need to get users into the store, though.

Much smaller filesize for vendor.js, although we'll have to see if all
the intervals are ok.