* Replace hardcoded strings using translation json file
This introduces a new "translations.json" file under app/static/settings
that is loaded on app init and uses the user config value for interface
language to determine the appropriate strings to use in Whoogle-specific
elements of the UI (primarily only on the home page).
* Verify interface lang can be used for localization
Check the configured interface language against the available
localization dict before attempting to use, otherwise fall back to
english.
Also expanded language names in the languages json file.
* Add test for validating translation language keys
Also adds Spanish translation to json (the only non-English language I
can add and reasonably validate on my own).
* Validate all translations against original keyset, update readme
Readme has been updated to include basic contributing guidelines for
both code and translations.
Federico Torrielli
Ben Busby