trunk: standardizing all perl and python scripts to start with a shebang /usr/bin/env perl|python, and to be executable.  Minor script change to train_mono.sh to print better info in case of error.

git-svn-id: https://svn.code.sf.net/p/kaldi/code/trunk@5110 5e6a8d80-dfce-4ca6-a32a-6e07a63d50c8