Bridge with support for pressure

[rieder]

Bridge uses get_gravity_at_point for each "kicker system" to determine the kick acceleration on each particle (note that in #556 we discussed renaming this to get_acceleration_at_point).

It would be nice if we can find a way to support a get_pressure_at_point function, for example to bridge two SPH codes working with different settings/resolutions.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 365 days if no further activity occurs. Thank you for your contributions.