Added url mappings for login and logout
added settings for login and logout urls
HTML page for user login. Fixes #90
added login form
added logout link
Added methods for user login and logout. Fixes #90
Styling adjustments for user logout link to place it to the right of the GW logo
Fixed problem of preserving the url accessed in case of authentication failure
Merge branch 'master' into inventory-user-authentication

Conflicts:
	inv/inv/local_settings.py.template
Fixed bug with login urls. Default behavior directes toward 'accoutns/login' which is not in our urls. Added login url to @login_required decorators to fix the bug.
Merge pull request #94 from gwu-libraries/inventory-user-authentication

Inventory user authentication