'Set Languages' dialog suggestions

[rtonsing]

Not sure how much this is actually used now, but it could be valuable in the future for spell check, and PPtxt character & scanno checks.

1. Show current value
2. Show hint for format - 2-letter, space delimited
3. Disallow invalid values - limit to 3 chars, or internal list (487 languages)?
4. Perhaps a link to a reference - https://www.loc.gov/standards/iso639-2/php/code_list.php?

[windymilla]

Thanks - I'll put this to "future feature" as GG1 has coped OK with it for many years, so not vital for the first release.

Other notes:

1. Currently shown in the status bar.
2. Actually, any lowercase word (including underscores) is permitted, and multiple languages can be separated by any non-word character, e.g. en+de or fr,no or en_us esperanto
3. Something like this has been suggested by @srjfoo (in fact that it should only permit languages for which you have a language dictionary installed), but at the moment I'm hesitant to restrict it like that. We only ship a few dictionaries with the release, but the user can make a dictionary themselves and name it however they like. An argument in its favor is that the first language named will end up as the "lang" in the HTML. So, I'm still undecided.
4. I think such a link should go in the manual, if anywhere - but since the user will also have to create a dictionary with a matching name, then as mentioned above it's not really too important what they call it, unless it's one of the few we ship.

GG1 also has the concept of language-specific labels, e.g. the word for FOOTNOTES. GG2 doesn't have that yet, but noting it here as another feature that is language-related.