Langpack fixes

* Fix filtering; broken by attempted reuse of generators.
* Make khan academy data download more robust.
* Make sure that all resources are refreshed in language packs, just not updated online; change paramters to reflect `update` logic.
* Merging some other style differences made while editing code.

Note:
* 26fe260 and a8c73a1 should be cross-merged to `release-0.10.3` when done here.