Add LineConsumerLogObserver
refactor python steps to not use log.getText
factor getText out of pbuilder.py
remove uses of log.getText from shell.py
factor getText out of Trial and HLint

This introduces rudimentary tests for HLint.  I don't have a sample of
output from this command, so I can't write any more comprehensive tests.
factor getText out of Mock and RpmBuild
remove regex_log_evalutator
remove fake log.getText method
notes to update documentation when everything is settled