Continuous deployment enhancements

Riff-Raff has been able to trigger a deploy on a successful build for some time. This pull request adds the ability to deploy when a successful build is tagged.

The use case next gen web have for this is to trigger a deploy to PROD when a successful build is tagged with approvedForPROD (or similar).

The interface has been modified such that the enabled checkbox has been switched to a tri-mode trigger option that can be successful, build tagged or disabled. A further field exists to ask for the tag when the build tagged option is specified. The database code was changed such that it can read version 1 and version 2 records, but will only write version 2.

The teamcity crawling has been reorganised into some more generic components for crawling teamcity builds and detecting changes. Extra listener interfaces have been added to listen for new tags.

The continuous deploy code has been reorganised to deal with the two different trigger mechanisms and act appropriately.