Change urls for reset password, forgot password and signup.

[sheetaluk]

Cleanup URLs and route names for reset password, forgot password and register.
https://trello.com/c/Yiraeqzs/408-logged-out-form-url-changes-and-redirects

Depends on:
hypothesis/h#3651

To test:

• create new user
• change email
• change password
• log out and log in with new password
• forgot password and reset it

[robertknight]

I've tested out this branch locally with the corresponding h service branch. All looks good. Just waiting for the H service branch to be merged first.

Note that any new release of the browser extension will also need to wait until the H service is deployed with these URL changes.

[nickstenning]

LGTM.