Don't include calculated area in unchanged bottleneck detection. This makes BN imports considerably faster. The only downside is, that when die waterway area changes there is no easy way to recalculate the areas of existing BN. But the semantics in that case are somewhat hard anyway (think of historization for the old area) so this should be ok.

teichmann@intevation.de = sascha.teichmann@intevation.de
bernhard.reiter@intevation.de = bernhard@intevation.de