Added ability to upgrade plugins and cleaned up some views accordingly for #953
Merge branch 'master' of github.com:concerto/concerto

* 'master' of github.com:concerto/concerto:
  If the date is empty, don't attempt to set it.
  disable alpha channel from pdf to png conversion
  disable alpha channel from pdf to png conversion
  use correct english plural forms
  clean up activity mailer translations for #838
  clean up translation plurals for #888