Add URL prefixes for Login and Edit buttons

(part of unmerged patch from https://github.com/jsbin/jsbin/pull/1450)
Add root prefix to missing links
Initial version of beautify
load beautifiers on demand
Better lazy Loading and code management
Add working 3-key keybindings
more precise file urls, remove excess function
Add explicit link to exit history view. Closes #2177
- add link markup in history view header
- add style to link similar to .url class
- add JS to reload current view
Better handling of user prefs
Merge pull request #2196 from jsbin/JonathanWolfe-beautify

@Jonathanwolfe beautify PR
Merge pull request #2152 from mattdsteele/url-prefix-fixes

Better support for jsbin running under a URL prefix
Add URL prefixes for Login and Edit buttons

(part of unmerged patch from https://github.com/jsbin/jsbin/pull/1450)
Add root prefix to missing links
Initial version of beautify
load beautifiers on demand
Better lazy Loading and code management
Add working 3-key keybindings
more precise file urls, remove excess function
Better handling of user prefs
Don't reload to show panels

- When the panelVisible class is applied, correctly hide the history (via css)
- Instead of a reload, get all the panels, check there's code, then show that panel