Fix dump option. Add enum for dump option

dump=2 was not documented on rt-slam website. Usage got from RT-SLAM's
demo_slam.cpp.
Add code to wait until ros time is ready.

Needed to work online from bag files.
Get the correct start_time if working online

Also needed to be able to run online from a rosbag file.
Remove wrong code to set timestamps_correction

It should be set by a configuration parameter on the main file.
Give time for the hardware to read some data from the topics

If we don't wait sensor manager will fail (segfault) because there'll
be no data available when trying to getNextDataToUse().
Stop the program if using dump and replay no slam until we fix a bug.
Remove time limit when processing the images.