Support a preference to choose an explicit locale

[Adam Winer]

Handy for my testing, and there are users whose default system locale doesn’t match how they want to handle birding.

[scythebill]

Resolved Issue #530: Support a preference to choose an explicit locale

Requires a restart to take effect. (Most of getting the local in place immediately is easy, but system menus and the taxonomy chooser are slightly more annoying. Took the easy way out.)

→ <<cset 6d82fa9c2f17>>

[scythebill]

Fix Issue #530 when the chosen locale is English. I misunderstood how locale inheritence works when there's a miss on an explicit locale - it actually reverts to system locale before using the default resource bundle.

→ <<cset 51032355a96e>>