Added try-catch blocks around parse xml calls in the Project::open function,...

Added try-catch blocks around parse xml calls in the Project::open function, so errors/warnings are now output to the Warnings tab in the GUI.  Fixes #4488.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/branches/ipce@7218 41f8697f-d340-4b68-9986-7bafba869bb8