Merge branch 'refactor-frontend-plugin-builds' into plugins-extra-static-content

* refactor-frontend-plugin-builds:
  Grunt-watch now works for plugin code too
Allow plugins to expose additional arbitrary static content
Merge remote-tracking branch 'origin/master' into plugins-extra-static-content

* origin/master:
  Simplified string checking for imports in webroot access test.
  Add a new test case to access the webroot, in order to increase coverage.
  Fixing dialog issue on base page and cleaning up vestigal events.
  Fixing a bug due to improper routing around multiple dialogs
  Fixed erroneous error message confusing question mark with dollar sign.
  Send file mime type when downloading
  Added check for metadata key containing question mark, plus a test.
  Fixed style errors breaking the pep8 style tests.
  Added some documentation of metadata exceptions and metadata in general.
  Added explicit error response in case of a period in metadata key name.
Merge remote-tracking branch 'origin/master' into plugins-extra-static-content

* origin/master:
Merge pull request #162 from girder/plugins-extra-static-content

Plugins extra static content