Add tests to debug functions, fix identified error & add ability to log raw messages

CRM-18212 requires the possibility of logging queries without timestamp information. The PR for this issue adds that functionality (without calling it at this stage) and also adds tests for that functionality & existing functionality and does some tidy up. In the process I found a bug in the existing debugLoggerCaching causing an e-notice & non-caching.

Note that this code is not a functional change as no existing functionality should be changed, although it does expose an additional logging parameter - the logFormat parameter. This parameter is only called from the tests until CRM-18212 is implemented