DB now stores user at host in events table too.
Tidy and tweaks.
Prevent creation of a new run db updater thread on reloading the suite.

This caused a left-over process on shutdown after reloading a suite.
Closes #295.
Merge pull request #298 from hjoliver/295-extra-thread-on-reload

Prevent creation of a new run db updater thread on reloading the suite.
Merge pull request #296 from arjclark/db-extend

Add user@host to task events