Simplify localization

Created by: julianhess

• Print diagnostics for RODISK mount failures: since we are intentionally suppressing nonzero exits and error messages (since these can commonly arise nonfatally), we need a way of reporting what went wrong if things actually do fail
• Greatly simplify prepare_job_inputs() in localization base class. Previous logic was convoluted; new code reads much better
• Raise explicit errors for files with the same name in the inputs directory. There is no elegant way to recover from this, so we just raise an informative error and exit.