Random string generator to support tests

Version:   2014.1009.53
Change-Id: Id55776506864bbfdac356cfb448393de2b558c86
tests for CrawlConfig.new_logger()

Version:   2014.1009.54
Change-Id: Ic26e6783d384e6cfc84a95ae21a639ad7cf13482
tests for CrawlConfig.log()

Version:   2014.1009.55
Change-Id: I61edc5cd944e485d3a050b46f1ac2d9530c71905
Don't open a new logger if one is already open

Version:   2014.1009.56
Change-Id: I0d01b097e0d5c07ca6bacf26d5f6e235a23c1d4b
Ensure the logger only has one handler

Version:   2014.1009.57
Change-Id: I35c2cef9dd3b35ae23bafb854b2aa943b11002cd
Explicit error handler for logger no longer needed in tests

Version:   2014.1009.58
Change-Id: Ic2d8ecd77a640f517f4d8bbfbda601696e466f58
raiseError requires an optional argument

Version:   2014.1009.59
Change-Id: If92c6acf59f322e17ba5a4f64d071b942ec73dba