+ Adapt language selection menus to the languages supported by the grammar.
+ Add translation quality colors to the links to alternative translations.
+ Also added more country codes in langcode.js (needed for speech synthesis
voice selection).
The background color of the translation changes to pale green, yellow or red
according to the quality.
Two types of quality indications are supported:
+ From the grammar: linearizations starting with "+" or "*" are assumed to
be of high or low quality, respectively.
+ From the parse tree: if the root function is "?", then the translation is
assumed to be of low quality.
If no quality indications are detected, medium quality is assumed.
