Relations and nodes can be const, as their buffer is read only.
Ways need to be writable, so we can add node locations
directly in the object. Hand them around as pointers to
make it clear they are mutable.

Don't go through the conversation into a geos geometry
but use our new wkb reader instead.

Role out our own wkb writer class instead of using libosmiums
internal implementation details. Allows a bit of stream-lining
and removes some of the hacks added to the libosmium copy.

Go back to printf conversion because std::to_string() does not
have sufficient precision.

No longer needed. Using libosmium types now.

Get roles and ids directly from the relation member list,
avoiding intermediate id lists and additional loops through
the members.

Postgres returns wkbs in hexform whereas the parser expects a
pure binary form. So convert before usage.

Geos is no longer required, or needed by CI

This includes the custom modifications in the official
libosmium branch.

 - way_area should not appear in hstore column in roads and
   line table
 - when using -G simple polygons should still be of type
   POLYGON

Changes are mainly due to broken polygons not being added anywhere
and a more eager line merging algorithm for routes.