20220107b_jdannberg

Fixed: Boundaries with tangential velocity are no longer taken into
account when checking if a boundary is an outflow boundary, which is
important in the case where temperature or composition are only fixed
on inflow (but not outflow) parts of the boundary. The old behavior
led to temperature/composition sometimes not being prescribed
correctly, especially in the case of spherical geometries.
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(Juliane Dannberg, 2021/07/07)