Merge pull request #46 from wtsi-npg/master

pull from master to devel (tag 74.3 )
Remove meta porgramming BUILD method to fix memory leak - fallback to more basic method of wrapper methods for all delegated methods.
Create readonly list of delegated methods from hash instead of function
Merge pull request #47 from dkj/devel

Mem leak fix
Changes update
Merge pull request #48 from wtsi-npg/devel

memory leak fix