[Rock-dev] fix in sonar_tritech task

[Sascha Arnold]

Hi,
the limit properties (leftLimit, rightLimit) of the sonar_tritech task 
were inverted in relation to the angles of the output samples.
This is fixed now.

This affects all who are using the tritech sonar in non-continuous or 
better to say ping-pong mode.
The angular range of the sonar if from -PI to the right to PI to the 
left. A limited scan range is defined from the left limit to the right 
limit. Like from leftLimit = 0.75*PI to rightLimit = 0.25*PI, which will 
result in a 90° scan range to the left.

Sascha