Add core model_tests.py and view_tests.py

[woanchang]

1. For the unit test for models and views of core application, the following directory and files are added.

        a. core/tests directory
        b. core/tests/__init_.py
        c. core/tests/model_tests.py
        d. core/tests/view_tests.py
   

2. The following initial data files are modified.
   a. core/fixtures/initial_data.json
   b. maps/fixtures/initial_data.json

3. Steps to run unit tests:
   1) Set the user and password for DATABASES in settings.py for the user with 'create' permission.
   2) comment out 'south' in INSTALLED_APPS of settings.py
   3) Run Postgres server
   4) Run GeoQ server
   5) Run the following command on a terminal window:
   python manage.py test core -v2