Improvements to the permalinks UI

Closes #4454

* Relies on Flexbox more heavily
* Adds JS to simulate how it should work
Fixing logic for editors deleting themselves

no issue
- no user is allowed to delete their own account
Merge pull request #4474 from ErisDS/profilefix

Fixing logic for editors deleting themselves
Version bump to 0.5.4
Reverting mysql to 2.1.1

- Unfortunately mysql has changed the way it handles the charset setting such that
it now causes encoding issues on many setups where 'utf8' is apparently not the
correct setting.
- We need to revert this upgrade until the issue is fixed or we have a way to handle
it nicely for our users.
Merge pull request #4475 from ErisDS/revert-mysql

Reverting mysql to 2.1.1
Version bump to 0.5.5
Update Tags Management Markup

References #4248

- Updates the markup & classes for the tag management settings menu, as they've fallen behind now we've renamed the 'right-outlet' to 'settings-menu'
Merge pull request #4480 from PaulAdamDavis/update-tags-markup

Update Tags Management Markup
Merge pull request #4469 from PaulAdamDavis/permalink-improvs

Improvements to the permalinks UI
Merge pull request #2 from TryGhost/master

更新