sensor_placement: some updates and experiments concerning runtime-improvements. however this is work-in-progress and still buggy. needs to be tested and reworked
sensor_placement: visualization bugfix
sensor_placement: removed index-bugfix in getTargets-function which led to wrong coverage-calculation and some by now unnecessary functions
sensor_placement: some code-clean-up
sensor_placement: occupied cells are now forbidden as new sensor-position
sensor_placement: some modifications for configurations with big sensor opening angles
some typos in comments corrected