CDB-23 #close Removes welcome to 2.1 message.
Merge branch 'develop' of github.com:CartoDB/cartodb20 into develop

* 'develop' of github.com:CartoDB/cartodb20:
  Add comment about why table.set_triggers drops a trigger
  [importer] Make Downloader use a temporary directory
  load dropbox key from config (removed hardcoded one) refs Vizzuality/cartodb-management#3139
  Drop varnish-invalidation triggers from user tables to tablemetadata
  Adds placeholder for dropbox api key on app_config sample
  [importer] Set error code in DataImport as reported by the importer's results data structure
  Adds new frontend config for dropbox
Fixes userstat spec