Adding ability to run tests without libmesh configuration.

This code adds a way for a code to ignore errors when finding options.
This would solve issue #4153 
If there is a better way to push the option into util.py, I can rewrite that portion.

A code can now do something like:
argv = sys.argv[:]
argv.append('--ignore-option-errors')
TestHarness.buildAndRun(argv, app_name, MOOSE_DIR)

to ignore the option errors.
I'm not sure I like this solution. If the libmesh_config file isn't found we should probably just cleanly return the set containing "ALL" from each of these routines, or better yet one of these routines that all of the others use. Instead, this solution just conditionally removes the exit condition allowing it to fall through doing things like failing to open files or running commands and leaving the return set in a somewhat unpredictable state.

As I look over this changeset it looks like at least one or more of these routines needs to be refactored anyway to use getLibMeshConfigOption. I can take a whack at this unless you want to.