Merge pull request #3 from wtsi-npg/master

pull from wtsi master to devel post release 47.0
when using and copying an existing cache directory copy everything

(instead of restricting to npg directory)
try to create samplesheet if it does not exist, even if copying cache
Merge pull request #4 from dkj/devel

Cache copy & samplesheet generation tweaks
Add tests and comment data for enhanced samplesheet creation
Merge pull request #5 from dkj/devel

Add tests and comment data for enhanced samplesheet creation
Changes update
Merge pull request #6 from wtsi-npg/devel

pull from wtsi devel to master to create release 47.1