Force full page reload on language change

[fozziethebeat]

Fixes #1287 by reloading the page every time a user changes their language. When a user changes their language during the a task page, it will re-fetch the task and show either a proper task in their language or show that none exist for that task type.

[othrayte]

Won't forcing the user to change task potentially throw away the content they have been writing. We currently tell the user to switch language (in a popup) if we detect it doesn't match the language that it will be submitted as.

[fozziethebeat]

Note: we discussed this a bit in discord and agreed with this sledgehammer solution. When we have to deal with intentionally multi-lingual tasks, we'll think about that more carefully.