Rename "areas" to "locations"

[jgaehring]

In the Tasks module, I need to rename both internal references and strings in the markup to reflect how areas are now considered location assets in farmOS 2.x. I'm going to hold off on this until the General Release b/c it's really not an issue with FK core, so much as with the module itself. It will also require changing many strings that have already been translated, and I still haven't figured out how that whole l10n mixin/Vuex module needs to change for 2.x (#456; I'm pretty sure I'm going to punt this to the beta milestone). Finally, since this touches on UX, it could pay to hold off until I finally overhaul TasksEdit (#408).