Make URLs more consistent, refactor libraries/releases

[daveoconnor]

This is related to ticket #1360

URLs are now consistent across releases and libraries pages, docs pages urls remain the same after discussion.

This is a big change, so testing would be appreciated and it should be merged after the next release so we can test it locally for a time.

The code is now cleaner with a lot more shared elements, version selection templating, setting of current and selected version data in a mixin used on multiple views in a cleaner unified way now we don't need to account for kwargs and query params.

A bonus of all this is most of the pages load faster (9x faster is the best result, same speed is worst, most in the 20% to 50% area).

There's probably some scope for improvement there if we want to chase that later and in the simplification of the version dropdown data population.

[GregKaleka]

There's probably some scope for improvement there if we want to chase that later

Worth collecting your ideas on this in a ticket while it's fresh?