move quantities, units, and flatten method to iris-common
remove flatten method from SedBuilder
findSherpa now returns the Sherpa SAMP ID everytime it is called
fix clients of findSherpa and flatten methods
fix issue #30

ExtSed can now be made 'managed' after they are instantiated.
SedlibSedManager now makes an ExtSed managed (if it
was not) upon adding it to itself.
Merge branch 'develop' into feature/integration
Complete integration under model components #41

Also fix #54