tweak log4php file:line column to optionally ignore log4php wrappers and optionally shorten file path

[simonhf]

Inspired by [1]. Useful if log4php is itself wrapped by a caller class which you do not want showing up in syslog as the file:line. Plus, if file is unnecessarily long then this patch allows the path to be shortened.

[1] http://stackoverflow.com/questions/15219327/php-log4php-dynamically-set-fileline-column

[kategray]

@rgoers Like the other commit, looks good in theory, but I'd like to get a unit test up to make sure it's behaving properly before committing this to develop.

[rgoers]

OK. Please go ahead with that.