Merge remote branch 'origin/feature/7464_remove_orphaned_definition'
Merge remote branch 'origin/feature/7483_remove_runoldpythonscript'
Merge remote-tracking branch 'origin/feature/5875_ConvertToMDHelper'
Merge remote branch 'origin/feature/7033_qtassist_dev_dependencies'
Merge remote-tracking branch 'origin/bugfix/7351_SofQ_isBroken'
Use more specific Nexus name instead of HDF in file loaders

* Rename HDFDescriptor to NexusDescriptor
* Rename {HDF,NonHDF} -> {Nexus,Generic} in FileLoaderRegistry
* Rename DECLARE_HDF_FILELOADER_ALGORITHM ->
  DECLARE_NEXUS_FILELOADER_ALGORITHM

Refs #7461
Make the IFileLoader interface a template. Refs #7461

This avoids having to declare a new interface when a new loader type
is added.
Merge branch 'feature/7461_rename_hdfdescriptor_to_nexusdescriptor' into develop