After saving a custom query, redirect to its results page

Summary:
Ref T2625. Currently, after saving a query the user is redirected to "/search/", which isn't especially useful. Instead, redirect them back into the application they came from and to the query results page.

Also, query hashes may contain ".", which does not match `\w`. Use `[^/]` instead.

Test Plan: Saved some custom queries.

Reviewers: btrahan, blc

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2625

Differential Revision: https://secure.phabricator.com/D6055