Fixed bug with creating cube with attributes whereby Process::SetOutputCube...

Fixed bug with creating cube with attributes whereby Process::SetOutputCube attempted to set attributes after opening.  Fixed bug in Process with cubes not being properly added and deleted by adding new method AddInputCube() and AddOutputCube(), which handles cube ownership.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@4138 41f8697f-d340-4b68-9986-7bafba869bb8