Made a small modification to the code in mergeNetworks(...) that created a new...

Made a small modification to the code in mergeNetworks(...) that created a new control network for each file in the file list. FileList's overloaded '[]' operator that was used inside of the call to Filename's constructor confused the compiler on Ubuntu10.04 systems. References #311.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@2974 41f8697f-d340-4b68-9986-7bafba869bb8