Update GET helper function, add custom columns to create profile

[cmdelrio]

1. Update GET helper function - There was a small bug in the logic for get endpoints where pagination is controled with a "num" page indicator. In short, line 140 was returning false when it should have been returning true!
2. Correct phone_numbers aspect of get_profiles - turns out mobile commons accepts a comma separated string of phone numbers, not a list.
3. Added the option to write custom column data to profiles in the create_profiles method. Also updated documentation to indicate that the create_profiles method can also be used to update existing records. Considered creating a new method all together for update_profile, but it seemed a little bit redundant...

[jeffjrodriguez]

LGTM

[shaunagm]

This looks straightforward, approving

[cmdelrio]

Thank you @jeffjrodriguez and @shaunagm !