#439: Add unit test to verify downloading a file authenticated as UserB using a signature generated for UserA fails
#338: Added unit tests for downloading principal pictures and verifying the multiple permutations that parameters can be passed in.
Merge branch 'master' into issue-439

* master: (42 commits)
  Changing grouping for adding members
  Fixed config file
  Minor doc fixes
  #502 - PR followup
  # 502 - Changed the actor and target for group-add-members
  Minor docs fixes
  #502 - Add tenant information to each activity entity
  README fix
  Updating README
  #404 - Resolving path to clean as we cannot output a path with a double slash.
  #500 - Not creating an activity if no text has been editted on publish.
  #500 - Passing the user's language on to Etherpad
  #500 - Fleshes out the Etherpad section in the README
  Minor test clean-up
  code review issues, actually test search, and fix the search
  add test for mime type property
  only add _extra.mime on 'file's
  add mimeType to content searches
  #472 Cleaned up image scaling in the preview processor a bit.
  Change etherpad port to 80
  ...
#493 - Create `removeContentFromLibrary` method in ContentAPI

Content can now be removed from a principal's library via the:
  /api/content/library/:principalId/:contentId
endpoint.

The discussion module has been slightly refactored. Some of the methods
have been moved over to the authz and library modulse and 
have been generalized.

`removeContentFromLibrary` relies on the same APIs as the 
`removeDiscussionFromLibrary` API.
Issue #484 - Added a testcase for actor->object and actor->target tenant boundaries

* Checking the visibility of target users that we're sharing with.
* Splitted out the tenant sharing tests into a separate file.
* Moved the createMultiTenantPrivacyEntities to the tests utility.
Merge master in issue-338 (profile pic test coverage).
Merged master in issue-493-removeContentFromLibrary
Merged master in issue-338 (bump in testcoverage for picture cropping).
#514 - Not generating a collabdoc-edit activity when no real update happens.
Added an autoOrient utility in oae-util/image

Rather then adding autoOrient on all of the ImageUtil methods, I've added
an extra method that can be used for this. `autoOrient` simply brings
to much overhead and a performance degradation to execute it on each
image operation.

For example, doing an `autoOrient` once on the source preview image rather
then on each single one, results in a performance improvement of around
36 percent.

I've also added `autoOrient` to the profile pictures so that they can be
displayed correctly in the browser.
Better handling of bad input for remote preview images

We're now better handling flickr, slideshare and vimeo inputs.
If an image has no thumbnail, it will be ignored.
PR followup on auto orienting

ImageUtil.autoOrient now takes 2 optional arguments
 * removeInput === true:   This will unlink the input image.
 * outputPath 				Specify where the output should be written to.
Added the medium preview uri/url to the revision.
Exposing discussion removal from library as a DELETE rather than a POST.
All preview images are now jpgs as they are smaller and faster to generate.
Merge branch 'issue-514-dont-generate-activity-collabdoc-on-create-edit' of git://github.com/simong/Hilary into issue-514-dont-generate-activity-collabdoc-on-create-edit
Merge branch 'autoOrientImprovement' of git://github.com/simong/Hilary into autoOrientImprovement
Returning the full revision object when restoring a revision
add etherpad-lite dependency to chocolatey.config

also add some clarification to the docs about what chocolatey does
and doesn't do
Merge branch 'issue-523-restoreRevisionProfile' of git://github.com/simong/Hilary into issue-523-restoreRevisionProfile