Implement minimal task manipulation

Why is this change necessary?
To obtain add/deletion of tasks with minimal error handling of Google
Calendar synchronisation, so as to acheive minimal program functionality
before V0.0's deadline tomorrow.

What side effects does this change have?
Messsages due to errors in Google Calendar synchronisation are not
shown.
Remove log file

Why is this change necessary?
To prevent tests from failing unnecessarily; tests will check for
existence of log files even when they're not purposefully created.