Add Neo layout keyboard for English

This cover [Bug 998299](https://bugzilla.mozilla.org/show_bug.cgi?id=998299)

[Neo](http://www.neo-layout.org/) is another layout for keyboards.

**Note**: Since Neo request at least 11 keys in each line this is a adaptation
of it to mobile devices (a adaptation to Android is available at
https://play.google.com/store/apps/details?id=com.anysoftkeyboard.languagepack.neo2&hl=en).