Imported events update

[cryhot]

This answers the same issues as pull request https://github.com/insanum/gcalcli/pull/584#issuecomment-839376331 (issues #492, #583), but actually updates the event (similarly to the google calendar "import" feature) instead of creating duplicates events or returning an error.

When using the command import on a .ics file with a specified UID, use the import method instead of the insert method. I've tested it and it works as intended (the event is replaced if already existing in the specified calendar).

Thanks to @tcheinen for having a first shot at this issue.

[MarkoSchuetz]

What is keeping this from being merged?

[cryhot]

Some function has been renamed, I've updated it in my branch, all conflicts should be resolved now.

[vincesherman]

This is a great solution; currently I import my 'work' calendar into my google calendar by importing an ICS daily, and manage duplicates by deleting everything from my google calendar before importing the ICS.

[yarikoptic]

This is promising! I just was informed that I had caused a large group of ppl getting duplicate notifications since my calendar got all them as guests on my "copy" of an event which I had imported twice (was updated). I guess this solution could have prevented it (didn't try yet).

@insanum - any chance you could have a look and provide feedback and/or merge?