Allow elogEntries to be built incementally

Originally for SCATTER-30
Also allows images to be added within blocks of text rather than as a list at the end.

Previous functionality should be unaffected.
Fix for previous commit (946fd4501fb845bf87) to prevent new property being required in java.properties

If you need the incremental entries, add:
gda.elog.imageurl=http://rdb.pri.diamond.ac.uk/php/elog/cs_logonlyimageupload_ext_bl.php
to your java.properties
Merge remote-tracking branch 'origin/8.38' into 8.38.mt
GDA (8.38.mt cherry pick from master) Changed NexusDataWriter to use SrsDataFile object when writing srs files. *Still needs work*

Breaks some functionality. May be restored for 8.40. See TODO in class.

Conflicts:
	uk.ac.gda.core/src/gda/data/scan/datawriter/NexusDataWriter.java
Changed SRS metadata class to allow reading from "metashop" collection instead of using its own internal collection
8.38 temporary fix until GDA-5974 is done.
Changed roi (HardwareTriggerableDetectorDataProcessor (DetectorDataProcessor.py)) .getDescription(), getDetectorID() and getDetectorType() to return " " instead of an empty string so we could write Nexus Files.
Correct property for getting file prefix

gda.data.filePrefix instead of gda.nexus.beamlinePrefix
Merge branch '8.38' of ssh://dasc-git.diamond.ac.uk/gda/gda-core into 8.38
FindableName widget: Change so that each tyme a charachter is typed into the box, an error is no longer generated. e.g. if there is a scannable named test and you type t then e then... you would previously get exceptions until the final t is typed.
Synoptic Product: Added ability to debug product.
Removed the listing of metadata when from meta_add and meta_rm (works very badly when used in scripts).
Fixed NXMetaDataProvider to better handle PyIntegers when creating group data.
GDA (8.38.mt 8.38 ONLY) Fix GDA-5956 - Deadlock in scan shutdown - Paul G has a better plan for master and 8.40
GDA-5956 (8.38 ONLY) Another temporary fix to deadlock in scan shutdown. PaulG has a better solution for master.
GDA (8.38) ScanBase now treats the property "gda.scan.clearInterruptAtScanEnd" as false by default restoring the 8.34 behaviour
Merge remote-tracking branch 'i07-prod/8.38' into 8.38

Conflicts:
	uk.ac.gda.core/src/gda/scan/ScanBase.java
Merge remote-tracking branch 'b16-prod/8.38.mt' into 8.38
Merge remote-tracking branch 'origin/8.38'

Conflicts:
	uk.ac.gda.core/src/gda/scan/MultithreadedScanDataPointPipeline.java
GDA: tiny forgotten bit of merge
Merge remote-tracking branch 'origin/8.38.mt'

Conflicts:
	uk.ac.gda.core/src/gda/data/scan/datawriter/NexusDataWriter.java
	uk.ac.gda.core/src/gda/scan/MultithreadedScanDataPointPipeline.java