Option to clip covered areas to entire study area rather than strata

[LHMarshall]

Currently each covered area is clipped to the stratum boundaries. If someone planned to survey across stratum boundaries (e.g. in seaboard surveys where the strata were just for design purpose) then it would make more sense to have an option to clip to the study area as a whole. This should mean more even coverage on stratum boundaries.

[LHMarshall]

Ignore last reference to this issue wrong issue number referenced!