First draft of OverlayManager UI
basic infrastructure for plugins:
* DSpace#loadPlugins() loads a given list of plugins
* DSpace#plugin() is to be called from plugin code to make itself known to DSpace
* DSpace#declareHook() is to be called from DSpace code to provide hooks for plugins
example implementation of a plugin.
removed remotestorage related code from widgetModal, implemented WidgetBar for plugins to hook into.
automatic plugin loading through config
implemented remotestorage plugin
list loaded plugins in user options
activate 'hello' plugin by default
don't put a dash between remote and storage. We don't want to substract storage from remote, but connect it!
removed defaulting deprecated 'remoteStorage' setting for users
world: allow feed types to be registered later
moved remoteStorage geo feed to plugin
removed default remoteStorage feed from config
log each plugin individually, as it is loaded.
finally moved all the other remotestorage related stuff to the plugin
removed remoteStorage paths from build.js
refactored plugin loaded to initialize plugins in the order given to loadPlugins()

This assures that widgetBar items always appear in the same order.
updated 'remotestorage' and 'hello' plugins to reflect change to dspace.plugin()
added 'widgetBarElement' hook to allow adding arbitrary views / elements to the widget bar.
removed deprecated WidgetBar markup from index.html / index.tmpl