geo/surface/planar: faster and better documented get_jb_distance() (+)
geo/surface/planar: faster and better documented get_jb_distance() (+)

1.83 times faster on a test with 2970 ruptures and 7200 sites

gem/oq-engine,larsbutler/oq-hazardlib,silviacanessa/oq-hazardlib,ROB-Seismology/oq-hazardlib,rcgee/oq-hazardlib,vup1120/oq-hazardlib,ROB-Seismology/oq-hazardlib,mmpagani/oq-hazardlib,gem/oq-engine,silviacanessa/oq-hazardlib,gem/oq-hazardlib,g-weatherill/oq-hazardlib,rcgee/oq-hazardlib,vup1120/oq-hazardlib,mmpagani/oq-hazardlib,larsbutler/oq-hazardlib,gem/oq-hazardlib,gem/oq-engine,g-weatherill/oq-hazardlib,mmpagani/oq-hazardlib,g-weatherill/oq-hazardlib,larsbutler/oq-hazardlib,gem/oq-engine,silviacanessa/oq-hazardlib,ROB-Seismology/oq-hazardlib,vup1120/oq-hazardlib,silviacanessa/oq-hazardlib,ROB-Seismology/oq-hazardlib,gem/oq-hazardlib,g-weatherill/oq-hazardlib,gem/oq-engine