Refactor geometry types

[Ylannl]

• Geometry types should not inherit from std::vector, this is not good practice
• should however implement a similar interface to std::vector, with size(), begin(), end(), front(), back(), operator etc
• use contiguous memory for coordinates
• maybe make number type (float, double) a template parameter (???)
• name the geometry types in accordance with CityJSON? or WKT? (poincloud, segments, linestring, surface (polygon), solid)
• how to handle semantics for solids?