Add description for ST_Force3D
Add description for ST_TriangleAspect
Update description and add image for ST_TrangleAspect
Add description and image for ST_TriangleContouring
Update description and images for ST_TriangleContouring
Update description for ST_TriangleContouring
Add description and image for ST_TriangleDirection
Add description and images for ST_TriangleSlope
Update ST_TriangleContouring
Add description for ST_Is3D

Conflicts:
	docs/dev/ST_Z.md

Fixes conflicts in #354
Fix category and section
Auto-format
Merge remote-tracking branch 'upstream/gh-pages' into m-351
Correct ST_Force3D @mlecoeuvre
Improve ST_Force2D @mlecoeuvre
Correct ST_AsBinary @mlecoeuvre
Correct ST_Is3D @mlecoeuvre
Correct ST_Z @mlecoeuvre
Fix 'Source code' links @mlecoeuvre
Temporarily remove ST_Triangle* doc [TO REVERT]

I am removing this temporarily so that I can merge #351 while waiting to
discuss the documentation of ST_Triangle* with @ebocher.