Add hash to collections table to minimize updating the DB unnecessarily

This impacts _sparcd_db.py_ **save_collections** and **get_collections** function, the _create_db.py_ file, and the **collections** table in the DB.

By adding a hash (generated by python) on the JSON stored a comparison could be made before updating the DB to see if a change is really needed.

The **get_collections**() function needs to fetch and store the hash value
The **save_collections**() function will need to:
1. generate a hash value for the JSON
2. compare it to the existing hash value if there is one
3. if the hash value is missing, or is not matching, save the JSON in the DB