Handle aborts due to >=100 errors

If there are 100 errors, LaTeX aborts in a new and special way.
Detect that error message and handle the fact that the file recorder
claims the PDF was output, but LaTeX in fact produces no PDF.
Maintain permissions when committing output PDF
Argument to print commands as they are executed
Skip output file commit if the file is byte-for-byte identical
Clean up LaTeXCommit implementation
Re-order command line argument help
Argument to control output file name
Simple test suite

A few of these tests are currently marked known-broken