Link handling fixes

 - Fix over-aggressive handling of circular links
 - Remove unwanted transitions on link display lines
Clean up some stray comments
Several updates, bugfixes, and improvements

 - Fix bugs intdroduced by recent API changes in editor.js
 - Add minor style updates to compensate for changes in editor.css
 - Improve text update efficiency
 - Make scrolling more fluid
 - Make minor updates to docs
Add command aliasing, minor bugfixes, and several small tweaks

 - Add a 'bounce' effect to a link line's end node when hovering over a
   valid link target
 - Showing link paths recursively is now optional
 - An invalid editor command will now clear the command bar, but not
   close it
 - Commands aliases may now be created (!!!). Infinite recursion is
   handled safely when aliases refer to each other.
 - Update Command class constructor to take a single options argument
 - Add safety checks in Editor.defineCommand()