A very simple mechanism for importing per-country language lists
from CLDR to ULS' langdb.
If I understand correctly, we only need languages spoken in a country
ordered by number of speakers. The CLDR data already has it and it should be
mostly useful.
Also added a utility function and a test.
Some tweaks to override the CLDR data are still needed:
* The data as it is omits some useful languages. For example, Amharic is not
listed in Eritrea.
* Some countries have a very large number of languages. Ideally it's right,
but is not practical currently, for example India with 75. Maybe
hand-picking or limiting the choice to top X languages can be useful,
but requires thought.
* Some language codes are standard, but different from Wikipedia practice,
for example "pa_Guru" (we just write "pa"). Maybe a mapping of codes
is needed.
Change-Id: I3c0cd5a9118997ba39a4f3695978e359f3de6956
ca411138c7