Split up wagtailadmin tests
Added wagtailadmin account management tests
These test the following:
 - Users can login and logout
 - Logged in users are redirected to dashboard (not implemented yet #25)
 - Account section works and users can change their password
 - The password reset functionality works
Added tests for unpublish view
Added permission checks to page views
Added tests for approve/reject moderation views
Added error tests for approve/moderation views
Improvements to search view tests
Removed unneeded import
Added tests for submitting pages to moderation
Added test for preview on edit
Added test for preview on create
Added test for content_type_use
Added test for preview for moderation
Added missing template
Added test for send email task
Merge pull request #273 from kaedroho/admin-tests

Admin tests