Remove discovery plugin

h/static/scripts/plugin/discovery.coffee

-class Annotator.Plugin.Discovery extends Annotator.Plugin
-  pluginInit: ->
-    svc = $('link')
-    .filter ->
-      this.rel is 'service' and this.type is 'application/annotatorsvc+json'
-    .filter ->
-      this.href
-
-    return unless svc.length
-
-    href = svc[0].href
-
-    $.getJSON href, (data) =>
-      return unless data?.links?
-
-      options =
-        prefix: href.replace /\/$/, ''
-        urls: {}
-
-      if data.links.search?.url?
-        options.urls.search = data.links.search.url
-
-      for action, info of (data.links.annotation or {}) when info.url?
-        options.urls[action] = info.url
-
-      for action, url of options.urls
-        options.urls[action] = url.replace(options.prefix, '')
-
-      @annotator.publish 'serviceDiscovery', options