When specifying 'FromTag all' the issues closed for the first tag aren't included

This should:
* Switch the FromTag argument to be a boolean switch AllTags argument to indicate that either only the latest changes should be included (AllTags = false) or all changes since the start of the repro should be included (AllTags = true)
* Update the `ByClosedIssues.GetReleaseNotes` to start at the correct place in time to include all items in a tag and thus fix #28

I've tested this on YouTrack and it seemed to get the right date ranges.