Redirect to original location after signup from links within pages (Henry)

[jjcmoore]

Basically, redirect users, after signing-in, back to page from which they were prompted to sign in from (within the page content).

On the View Issue page, there are "sign in" links, prompting the user to log in before they can vote/follow/comment on the issue. Currently these just redirect to the home page after signing-in, but it would be nice if they could be redirected to the original location (i.e. to the issue that was being viewed). It would also be good to have this implemented as a general solution, so this can be called from any other location that prompts for a sign-in within the content of a page.