Propagate parsing errors to application level

[pmpowers-usgs]

Presently, if errors occur while parsing source or GMM XML files, Loader.java logs the errors and exits. This leaves a stray log file in the directory from which a program was called, the name of which is unknown to the Loader class. We should instead propagate the errors, and rewrite the log file to nshmp-haz-error-tstamp (or similar), but leave it in the application calling directory. Also consider adding info about the results directory that may be invalid or just delete it altogether, assuming it's been created.