HPCC-2205 RoxiePipe logging to /c$/roxiepipe

Currently roxiepipe defaults to placing logfiles in the current directory,
making it difficult for OPs to locate them. This code change queries the
system log directory, and puts the (rolling) logfiles there

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>
Merge pull request #5030 from RussWhitehead/roxiePipeLog

HPCC-2205 RoxiePipe logging to /c$/roxiepipe

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>