Improve outlines

[bertt]

Outlines can be improved, for example

[mittermichal]

add check to GetSharedPoints that the 2 triangles can't be on same plane?

[bertt]

Testcase france building dataset:

bdnb-bc-FPEC-T1JW-4YD3

MULTIPOLYGON Z (((-1.421699899999999 43.643735699999986 60.451839381624225,-1.421701999999999 43.643754199999975 60.45180898666029,-1.421705699999999 43.643791299999975 60.451748343341656,-1.421708689586463 43.643820199340155 60.45170103971123,-1.42166610892875 43.64382193270137 60.451724175885175,-1.421657729150121 43.64372944988528 60.451874839609864,-1.421699014962898 43.64372721169453 60.45185328000349,-1.421699899999999 43.643735699999986 60.451839381624225)),((-1.421699899999999 43.643735699999986 64.55183938162422,-1.421699014962898 43.64372721169453 64.55185328000348,-1.421657729150121 43.64372944988528 64.55187483960987,-1.42166610892875 43.64382193270137 64.55172417588517,-1.421708689586463 43.643820199340155 64.55170103971123,-1.421705699999999 43.643791299999975 64.55174834334166,-1.421701999999999 43.643754199999975 64.55180898666029,-1.421699899999999 43.643735699999986 64.55183938162422)),((-1.421699899999999 43.643735699999986 60.451839381624225,-1.421699899999999 43.643735699999986 64.55183938162422,-1.421701999999999 43.643754199999975 64.55180898666029,-1.421701999999999 43.643754199999975 60.45180898666029,-1.421699899999999 43.643735699999986 60.451839381624225)),((-1.421701999999999 43.643754199999975 60.45180898666029,-1.421701999999999 43.643754199999975 64.55180898666029,-1.421705699999999 43.643791299999975 64.55174834334166,-1.421705699999999 43.643791299999975 60.451748343341656,-1.421701999999999 43.643754199999975 60.45180898666029)),((-1.421705699999999 43.643791299999975 60.451748343341656,-1.421705699999999 43.643791299999975 64.55174834334166,-1.421708689586463 43.643820199340155 64.55170103971123,-1.421708689586463 43.643820199340155 60.45170103971123,-1.421705699999999 43.643791299999975 60.451748343341656)),((-1.421708689586463 43.643820199340155 60.45170103971123,-1.421708689586463 43.643820199340155 64.55170103971123,-1.42166610892875 43.64382193270137 64.55172417588517,-1.42166610892875 43.64382193270137 60.451724175885175,-1.421708689586463 43.643820199340155 60.45170103971123)),((-1.42166610892875 43.64382193270137 60.451724175885175,-1.42166610892875 43.64382193270137 64.55172417588517,-1.421657729150121 43.64372944988528 64.55187483960987,-1.421657729150121 43.64372944988528 60.451874839609864,-1.42166610892875 43.64382193270137 60.451724175885175)),((-1.421657729150121 43.64372944988528 60.451874839609864,-1.421657729150121 43.64372944988528 64.55187483960987,-1.421699014962898 43.64372721169453 64.55185328000348,-1.421699014962898 43.64372721169453 60.45185328000349,-1.421657729150121 43.64372944988528 60.451874839609864)),((-1.421699014962898 43.64372721169453 60.45185328000349,-1.421699014962898 43.64372721169453 64.55185328000348,-1.421699899999999 43.643735699999986 64.55183938162422,-1.421699899999999 43.643735699999986 60.451839381624225,-1.421699014962898 43.64372721169453 60.45185328000349)))