285 - Back Button fixes

[bent0b0x]

Issue

285

Problem Previously, clicking the back button on the header would take the user to whichever page from which they had navigated, even if it was from another domain:

Work Done

• Add a route-change listener that stores the previous route in Session
• Have the back button navigate to a page using the following logic
  • If its parent template explicitly passes in a route the back button should navigate to, navigate to that route (e.g. the back button on the playlist page should always navigate to the list of playlists)
  • If no route was explicitly passed in, navigate to the previous route in Session
  • If no route was explicitly passed in and there is no previous route (e.g. user has just freshly navigated to Paratii profile), hide the back button completely
• This PR also includes refactoring the profile page to use the internal header that @jrgarou built

Demo

@jellegerbrandy @geckoslair @pedrocasa interested to hear your thoughts on this change.

[bent0b0x]

Also, thanks to @jellegerbrandy for the new test utils/helping establish best practices for writing the browser tests. Didn't find myself in timeout hell for this PR :)

[jellegerbrandy]

Great stuff, and many thanks for writing tests :-)