Added GetMeasures method. Network now notified when a points ignored status...

Added GetMeasures method.  Network now notified when a points ignored status changes for updating its cube connection graph (cube connections were not respecting ignored flags on points or measures).

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@2021 41f8697f-d340-4b68-9986-7bafba869bb8