[http-sessions] The HTTP sessions component is nearly finished (the
reauth needs a comm channel to multi-instance proxy)

    + Added the new HTTP sessions DB API methods
    + Added API and UI methods
    + Added necessary links to target page
    + Updated urls

The viewing of URL map is still incomplete (needs a somewhat complicated
ORM query)

Some possible changes:
    + Generate HTML for the sessions_view by JS (for more than 2
      session tokens per response) - inputs?
Merged upstream changes and removed trailing whitespaces and little PEP8