Added more optimised code, but sumgrid bathy still needs more work, see issue in comment in code
Fixed issue with land blocks in sumgrid bathy opt, and it seems to work well now, significant speed ups are obtained (an example run took 40 sec with optimised code versus 1100 sec with non-optimised code)
Optimised code for all three biases available using the opt flag, results deviate a little from non-optimised code because sensors are not allowed to be above water, and lands areas are handled differently