Add Lato fontface

[#45966695]

http://www.google.com/webfonts/specimen/Lato

Lato is distributed under the SIL Open Font License 1.1
http://opensource.org/licenses/OFL-1.1

Lato complete set fontface-kit downloaded from:
http://www.fontsquirrel.com/fonts/lato
remove extra copy of Open Sans

[#45966695]

There is still the open-sans fontface kit included in
src/vendor/fonts
Lato or Open Sans fontface selected in config.yml

[#45966695]

Specify either 'Lato' or 'Open Sans' as the default fontface
in config.config.yml:

Example specifying Lato:

:jsconfig:
  :fontface: Lato

The default fontface if one is not specified is 'Open Sans'.