Simple 3D buildings

[mojodna]

Building relations, per https://wiki.openstreetmap.org/wiki/Simple_3D_buildings

This does not yet handle recursive relations (type=building containing type=relation multipolygon members).

Relation members now internally require a true _type (Byte) column, rather than a synthetic one.

Snapshot arguments are added to way and relation reconstruction to reduce the number of elements processed when either snapshots are desired (from history) or when the input is a snapshot (no history).

• [ ] implement (or document the lack of) recursive relation handling
• [ ] ensure that relation member geoms always have a _type column
• [ ] test geometry reconstruction tools

[jpolchlo]

I had some private data checked in to the source tree that I had to blow away. If you are interested in keeping this PR live, can you rebase, @mojodna ? Also, probably worth targeting develop as the base branch while you're at it.

[mojodna]

This PR is probably addressed by the VP relations branch, since that includes more general support for relations (at the expense of quite a bit of runtime, which is why I haven't submitted it as a PR).