Extract forms metadata at server side instead of client side

Upon downloading forms, mUzima currently extracts Concepts, Locations and Providers IDs from forms, which takes a long time. For instance, it takes about 70 seconds to extract concepts from CDM Dispensary and Health center forms. It takes relatively shorter time to download forms than it takes to extract and store metadata.

To reduce workload on devices, the work of extracting metadata should be placed at the server side, so that mUzima only downloads the metadata.

This will be done in two sub tasks:

1. Add field to muzima forms table for storing metadata, and create logic to populate this field every time a form is uploaded / updated
2. Change the way mUzima works by updating it's logic to retrieve form metadata from server side