Fix to http://jira.diamond.ac.uk/browse/SCI-1392

Conflicts:
	uk.ac.diamond.scisoft.analysis/src/uk/ac/diamond/scisoft/analysis/io/HDF5Loader.java
Fixed append bug and added missing python version and test
Attempted fix to http://jira.diamond.ac.uk/browse/SCI-1341
Revert "Attempted fix to http://jira.diamond.ac.uk/browse/SCI-1341"

This reverts commit bd01cb1da92ee9f49d60261ae76a0141d0cc1578.
Proper fix for SCI-1341
Added python test of gradient of slice
Fixed issue with asDataset function for abstract datasets
Fixed problem with taking differences and gradients of views and added
unit tests
Added python test of gradient of slice
Merge branch 'gda-8.34'
Renamed new Nexus loader to avoid collision