Merge branch 'statistics' into administration

.meteor/packages

.meteor/versions

client/stylesheets/base.less

client/views/admin/adminStatistics.coffee

client/views/admin/adminStatistics.html

i18n/en.i18n.json

packages/rocketchat-lib/package.js

...s/rocketchat-lib/server/functions/getAvgStatistics.coffee

...ages/rocketchat-lib/server/functions/getStatistics.coffee

...ges/rocketchat-lib/server/functions/saveStatistics.coffee

...s/rocketchat-lib/server/methods/generateStatistics.coffee

server/lib/collections.coffee