HPCC-10292 ZIP from Zap has path info

Currently when zipping logfiles, paths are included as part of the zip, so you have something like

//10.0.2.15/var/log/HPCCSystems/myeclagent/eclagent.2013_10_15.log

This effectively hides the file in some ZIP browsers, so we should strip out the paths and just save the filename

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>