Update frames and topics

- /scarabID/odom_motor for TF frame and odometry topic
- /scarabID/base_link for base frame of robot
Changes to get laser odom working with AMCL

- Default AMCL params now work fine
- Don't broadcast tf from roboclaw node
- Don't publish useless scan from laser_odom
Periodically update local laser map if no movement

Previously, if robot sat still a single scan would be added and then the
map would fully decay at which point the robot would jump.  Now, when
decaying the map, if there haven't been any updates since the last
decay, use the latest scan to update the map.