adding support for "Daily Activity Summary" API call

[davoutuk]

Adds support for the Daily Activity Summary API call documented at https://dev.fitbit.com/build/reference/web-api/activity/get-daily-activity-summary/

[gcappon]

Thank you very much for your contribution! I really appreciate it.

Here's some changes/requests to be implemented before merging:

• Please use the convention of the package when naming your files, i.e., camel case.
• Please use a dedicated class to represent the url of a daily activity summary call. Suggested class name: 'FitbitDailyActivitySummaryAPIURL'.
• Can you please provide a short screen recording (e.g., the screen of the emulator) showing that your are able to fetch the data?
• Can you provide the console log resulting from a call using your code?

Thank you very much again.

[gcappon]

Hi there. Did you have the opportunity to work on the edits I mentioned?