Bugfix/health checks

[Phencys]

Added a 30 second timeout / 60 second kill timeout on the segment validator, to prevent it from running indefinitely.

Added a category of "health" checks to the logger module, to message various issues with the segment validator:

• The segment validator took too long and is killed
• The resulting XML file is > 100mb. (There is a set of test files that generate 2GB files of whitespace)
• The resulting XML is invalid XML

On health issues with the segment validator, segment validation is skipped for the remainder of the run.

This should address - at least a part of - issue #602

Also added some minor rewrites to address issues #612 and #614