added comments to track_file_tools
log_and_playback: using the localize pose from logs if available

if LocalizePose is available from the logs, then use it to get the
global transforms, otherwise use the fake localizer.

this way, one can choose to use the velodyne localizer, without having
to run it, and this does not require making its code available.
velodyne message filter: added an option to clear the collector
Merge branch 'master' of github.com:StanfordDrivingTeam/driving_public