GDA-5788 make the addData method public to allow plots to be added programmatically
prevent NPE
fix Javadoc and remove compiler warning
fix logic when deciding to plot or not lines based on the
ScanPlotSettings

There seems to be some duplication here which should be resolved, but
not on a branch.
add exception so that inheriting classes may throw them

this base class should probably be modified, but not in a release branch
Core - Add getNamedService to GDAClientActivator
Client - Add use of HelpHandler to JythonTerminal
HelpHandler - support gda_command topic types
Client - add help_contexts to client
HelpHandler - add support for using Eclipse Help system
prevent NPE as scanPlotSettings may be null at times
Merge branch '8.36' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-core.git into 8.36
BLXVIIIB-133 when switching to the Experiment perspective, make sure all dirty editors are saved.
BLXVIIIB-125 improve Simple Scan view usability and error handling
Merge branch '8.36' of ssh://dascgitolite@dasc-git.diamond.ac.uk/gda/gda-core.git into 8.36
CORE (8.34) Noted that TwodDataSetProcessor is extended by Eric's FlippingDevice from i06 and/or i07
Core - Fix bug in determination of event channel name registered by
eventserver
do not broadcast a PAUSE when the queue is emptied

This leaves the system in an incorrect state as it puts the ScanBase.paused flag to true, when it should be false. 

ScanBase.paused == true is when the running scan should be temporarily paused, so setting this when the queue empties is wrong.
always update UI buttons, do not only disable them, when Jython server status is changed
do not enable controls when command queue is empty

Also have the queue stop button greyed out when the queue is empty for consistency