geo/mesh: jb distance now uses minimum enclosing polygon
geo/mesh: jb distance now uses minimum enclosing polygon

which is convex hull for unordered mesh and union composition of
projections of all the vertical stripes of the cells for rectangular
ones

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