Make right column map fixed positioned

[samanpwbb]

Th right column map is now fixed positioned on http://www.openstreetmap.org/browse/changesets

Lets do the same thing on other pages that follow the same layout pattern:

• user profile
• browse pages

[tomhughes]

Browse pages no longer exist now #498 has been merged, so only the user profile remains affected.

[gravitystorm]

The user profile page now has a responsive layout. It might be nice to use some kind of position: sticky to keep the map in view when it's in two-column layout, however, the current version of bootstrap doesn't offer responsive positioning and so a sticky map would look bad in the single-column view.

I think this is a low enough priority that, in the meantime, this issue can be closed.