Field value display presentation improvements

 * Display mask char in password field

 * Disable line wrapping for field values

 * Make field values appear selectable
Improve presentation of field values

 * Remove borders below item title
   and account/password fields

 * Display labels underneath values

 * Display only the hosts for item locations,
   elide long URLs and make locations clickable
   links
Implement options to Copy and Reveal field values

Now that the password field is masked a 'Copy' option
is needed to make it copyable.

Implement the 'Copy' action for Chrome and Firefox
and the 'Reveal' action for all frontends.
Fix rendering of password mask chars in Chrome ext

The mask char literal was being rendered
incorrectly as the charset of the background
page was not set, although the charset of the panel
page had been set.

Set the charset for the Chrome extension background page
to UTF-8
Add unit test module for webui/reactutil