Add Drive resource and example.

Summary:
Add support for the Drive resource as described in the Google Drive API Reference [1].

[1] https://developers.google.com/drive/api/v2/reference/drives

Test Plan: Test units have been added for the Drive resource operations. An example is included which demonstrates fetching, modifying, hiding Drives.

Reviewers: dvratil

Reviewed By: dvratil

Subscribers: #libkgapi, dvratil, kde-pim

Tags: #kde_pim, #libkgapi

Differential Revision: https://phabricator.kde.org/D21838