Handle realistic size generate mcstas event files

[Anders Markvardsen]

When loading mcstas files containing more than about 200 MB event data block Mantid comes to a halt because of Nexus getData struggle.

Allow LoadMcStas to handle larger than 200 MB event data blocks

[Anders Markvardsen]

Can now load large mcstas nexus files. re #9137

Updated test do check that can the same results before and after.

Reading in blocks of about 50MB. This seems to work quite well on my windows system, but perhaps another value will could give a better performance

Note now that reading in part progress reporting could be improved. Not done here

Changeset: 1f5d0eb79f3445c4a9cc9d787ab171a05ef56fef

[Russell Taylor]

FYI: There's a gcc compiler warning from this - ​https://builds.sns.gov/job/ornl_clean_rhel6_develop/2983/warnings17Result/

[Anders Markvardsen]

Remove compiler warning. re #9137

Changeset: a2ec33d1f25ab9de182b782c69d79fbc825f82a9

[Anders Markvardsen]

To test:

1. Download: mccode_very_large.h5 from ​ftp://ftp.nd.rl.ac.uk/scratch/Anders/

2. check that it loads into MantidPlot using the Load button (on my developing machine this takes something like 3 minutes)

[Martyn Gigg]

I've checked that the file does indeed now load. I have created #9211 to deal with this.

[Martyn Gigg]

Merge remote-tracking branch 'origin/feature/9137_large_files'

Full changeset: ​9aab2dee4bf1e004e46d3f2ea6581b5d10dd1e7d

[Anders Markvardsen]

note in connection with this ticket the tread ​https://github.com/mantidproject/documents/blob/master/Design/EmbeddedInstrumentInfoNexus.md has been created

[Anders Markvardsen]

Ignore comment 10 made it to the wrong ticket

[Stuart Campbell]

This ticket has been transferred to github issue ​9980