[oshdb-filter] add more geometry filters

[tyrasd]

More advanced geometry-aware filters would be possible and perhaps useful to implement. Some examples:

• quantitative geometry filters
  • [x] length & area (already implemented)
  • [ ] perimeter → #436
• geometry structure
  • [ ] vertices (number of vertices of a line/polygon) → #436
  • [ ] number of outer rings of a multipolygon → #436
  • [ ] number of inner rings of a (multi)polygon → #436
• shape dependent filters
  • [ ] polygon squareness of angles (possible syntax examples: squareness:0.9 or shape:square(..0.9))
    todo: what definition of squareness should this be based on? :arrow_right: A Rectilinearity Measurement for Polygons ?
  • [ ] roundness of polygons :arrow_right: Polsby–Popper test
  • [ ] straightness of lines (see "curvature") below
  • …
• other geometric properties
  • [ ] curvature / tortuosity of lines
  • [ ] geometric complexity (think something like the number of vertices per length/perimeter; the iOSMAnalyzer has something called eqidistance which should go into this direction)
  • [ ] number of vertices of a line or polygon, number of holes in a (multi)polygon, number of outer rings of a multipolygon, number of geometries of a geometrycollection, etc.
  • …
• error detection
  • [ ] self-intersections
  • [ ] duplicate vertices
  • [ ] valid geometries (simple feature standard)
  • …
• …?

Some of the above are just ideas and would need to be discussed individually in detail: how are they defined? what comparison values / threshold can be applied?

Ideally, we would come up with a syntax what syntax which can be used somewhat universally for all/most of these.

This issue was originally posted at https://gitlab.gistools.geog.uni-heidelberg.de/giscience/big-data/ohsome/libs/ohsome-filter/-/issues/6