Merge pull request #95 from wtsi-npg/devel

pull wtsi devel to master to create release 75.0
Merge pull request #97 from wtsi-npg/master

wtsi master release 75.0 to wtsi devel
Merge pull request #25 from wtsi-npg/devel

pull from wtsi devel to my devel (release 75.0)
patch for samplesheet parser; switch live npg api base URL to a different host; removed depricated methods from npg::api::run_lane; simplify code for saving XML feeds to cache
Merge pull request #98 from mgcam/devel

switch live npg api base URL to a different host in order to separate human- and api-driven requests
patch for samplesheet parser
removed depricated methods from npg::api::run_lane
simplified logic for saving to cache in npg::api::request and removed unused save2cache methods
staging area indexes defined in single place