improve the sentry returner so that successful executions are also sent ...

...to sentry.

Before this PR only errors where sent to sentry, now also successful payloads. The returner has some (basic?) detection code which should be reviewed by someone with better knowledeg on how salt defines success/failure statuses.

Also I have expanded the pillar config options to include the ability to specify sentry tags by picking them out of salt grains. The purpose of sentry tags is to allow filtering and notification of messages in the web ui.