BLX-73 (8.40) Make beamcheck scannable extra names unique.

Also, add better reporting of status at scan start.
BLX (8.40) Fix PauseScanHandler logic & make it more obvious what it is doing.

This fixes the problem where you couldn't get out of a scan paused state
because it was running the scan idle logic.
Merge remote-tracking branch 'auto+dls_sw+i10+software+gda_versions+gda_8.40b+workspace_git/gda-8.40' into gda-8.40