Update npm
Fix caching of npm search results and only make one registry request on /admin/plugins

fixes #1488
Make npm registry access code more sane
Revamp /admin/plugins

- dry up the client-side code
- use the new saner API of pluginfw/installer.js on the server
- Improve UX: allow user to infinitely scroll to display their results
Don't leak event listeners in pluginfw/installer.js

fixes #921
admin/plugins: Allow people to sort search results
/admin/plugins:Hide ep_etherpad-lite in the list of installed plugins
/admin/plugins: Add progress indicators and report errors
Catch all errors in pluginfw/installer.js
Silence npm when using npm.commands.search
/admin/plugins: Make it display the same amount of plugins after sorting
/admin/plugins: Don't list installed plugins as available
pluginfw/installer.js fire callbacks only once
Install and uninstall plugins with style

- Don't block the whole page when installing a plugin
- allow people to search and install other plugins meanwhile

Why? http://i.imgur.com/XoX6uYS.jpg
/admin/plugins: Show some text if nothing is display otherwise
Remove plugin prefix in pluin lists and make links to plugins more clear
Disable search until registry is loaded and fix sorting by version

... and always display a scrollbar.
/admin/plugins: Fix infinite scroll for larger screens
/admin/plugins: If a user installs sth scroll up to the loading indicator
/admin/plugins: Fix for smaller screens