Updated and tested Get CustomFileds API, as well as Creating Address for a JSON Client API

1.Tested with Mambu 3.3. on staging
2. Corrected and tested getCustomFileds() API. Removed TODOs.

3. Tested creating address with Json API.
3.1 The address is created successfully in Mambu
3.2 Note this Issue: the address info is not returned with the create client API Response.  Need to use getClientDetails() to get all created info