Remove link to admin interface
Inherit OTIUser from AbstractUser

Extend from AbstractUser, rather than AbstractBaseUser

We get all the default functionality of the
django.contrib.auth.models.User class without having to reimplement
anything. This makes it easy to add additional custom fields/methods
in the future.

NOTE: This commit requires a 'DROP DATABASE transit_indicators;'
and then a re-run of the provision script
Add permissions for API views

There are two new viewsets, which inherit from ModelViewSet
  - OTIAdminViewSet
  - OTIBaseViewSet

This allows the settings/configuration views to be read-only for regular
users, and editable by admin, which is defined as having
is_staff == True

Default permissions are full access for regular users,
must be authenticated
Merge pull request #60 from WorldBank-Transport/feature/auth-permissions

Feature/auth permissions
Restrict datasources views to admin users
Add regular user to provision script
Add login splash page to OTI app

Login via functions on authService,
Token checked on each API request via interceptors
in the auth module.
Add user object to rootScope
Merge pull request #61 from WorldBank-Transport/feature/angular-login

Angular Login Page
Remove favicon
Merge pull request #62 from WorldBank-Transport/feature/remove-favicon

Remove favicon
Move source_file to separate class.
Add import functionality for demographic data

This adds a number of classes to track demographic data:
- DemographicDataSource: A shapefile providing demographic data
- DemographicDataSourceProblem: A Problem with a DemographicDataSource
- DemographicDataFieldName: The fields available for import from a
    DemographicDataSource
- DemographicDataFeature: Stores the values of the fields chosen by
    the user along with their associated geometries.
- OTIDemographicConfig: The configuration of the app regarding which
    fields from the shapefile are being used for indicator calculations.

It also adds two Celery tasks for dealing with shapefiles containing
demographic data:
- get_shapefile_fields: Generates DemographicDataFieldName objects based
    on the field names found in the shapefile, but does not import any
    data.
- load_shapefile_data: Loads the data specified by the user from the
    shapefile into the database; creates DemographicDataFeature objects.
    Removes any existing data before running, so only one set of data can
    exist in the database at any given time.
Remove currency from poverty_line.
Flesh out Celery task comments.