BLXVIII-165 resolve issue where the RealPositionReader was being used in both fly-scan types (ContinuousScan and ConstantVelocityScan) but only worked for one of them

This is because this class relies on the Epics Trajectory template being read out and this happened in ContinuousScans but did not happen in ConstantVelocityScans
avoid 'g.d.m.EpicsMotor - Error: illegal .{HLM,LLM} value.' message if dbr.isSHORT; use motor name in message otherwise
Revert "avoid 'g.d.m.EpicsMotor - Error: illegal .{HLM,LLM} value.' message if dbr.isSHORT; use motor name in message otherwise"

This reverts commit 9c644a34e9fd0f255e70d988d520f05282d8e7b8 which
caused .HLM and .LLM values on I04-1 to be set to 0. It transpires that
they are initially set to the correct values via
EpicsMotor.set{Max,Min}PositionFromListener(double {max,min}Position).
The problem is that EpicsMotor.{HLM,LLM}MonitorListener implementations
log the titular message in the first place, as dbr.isSHORT() returns
true, contradicting cainfo on the PVs!
MXGDA-2060 fixed.
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
Throw exception if adbase portname is not set in EPICS
Return empty NXDetectorData if plugin is disabled.
Return empty NXDetectorData if plugin is disabled.
Merge remote-tracking branch 'origin/gda-8.40'

Conflicts:
	uk.ac.gda.epics/scripts/epics_scripts/pv_scannable_utils.py
	uk.ac.gda.epics/src/gda/device/detector/addetector/filewriter/MultipleImagesPerHDF5FileWriter.java
	uk.ac.gda.epics/src/gda/device/scannable/EpicsTrajectoryScanRealPositionReader.java
	uk.ac.gda.epics/src/gda/scan/EpicsTrajectoryScanController.java