Refactor media uploading alert for featured images
Fix media upload error management
Better error management for uploads:

* Try to detect out of memory errors and show a relevant message
* Show an alert when uploads fail
Fixed help view controller

When there was a modal view present (e.g. error from the editor),
tapping on 'Need Help?' would do nothing.
Don't purge image files, unless the image already uploaded
Added unit tests for iOS5 rotation
Disabled unit tests for autosaves
Bump version to 3.5.3