Cloned dz3-scheduler-gcal module into dz3-scheduler-gcal-v3 to keep v1
and v3 code separate
Checkpoint: moving Google Calendar API from v1 to v3, work in progress:

- Moved logger to abstract superclass;
- Moved functionality possibly common to multiple protocol
implementations into GCalScheduleUpdaterBase;
- Implemented Calendar API v3 support - draft version, baseline for
future improvement;
- Adjusted test case for dependencies;
- Adjusted POM for dependencies.
Checkpoint: moving Google Calendar API from v1 to v3, work in progress:

- Removed no longer relevant username, domain, and password;
- Added client secrets (yeah, that's more secure for an Open Source
application);
- Removed no longer useful body of testAuth().