Flat table of all OSM objects

[XinWang1128]

Currently we distinguish between points, ways and relations and store them in different tables.

Alternatively we can store all object in a flat table, which would make it easier to map to triangles and then even more when trying to map back to tags, for example.

In such a manner, we identified that it might be difficult to add a new objects. However, with OSM data for now, we only take a snapshot and will just delect or ignore some object, thus will never add a new object. Maybe this will be different to other geospatial data.