Attempt to extract the log slurper from the MissionPlanner

Currently the only/best way to extract logs from the arupilot board is
to go through the (Windows-based) MissionPlanner app.  This is an
attempt to extract just the log-reading portions from the
MissionPlanner, to allow execution under eg OSX
Trying to fix log slurper
Fix log dumping and add erasing of logs
updated ignores