Need to add sleep(2s) after pco arm

http://jira.diamond.ac.uk/browse/BC-99
Ensure we get 1 exposure per trigger
Add TODO
BLXIIIJ-55 - Add function ls_pv_scannables

Function to list Scannables associated with EPICs PVs, the PV and the associated DESC field
    Usage:
    ls_pv_scannables()
Enhance ls_pv_scannables
Add ability to list scannable associated with PV