Add reader and writer to send points over sockets

[wonder-sk]

The idea is to create a reader and a writer that would pass point cloud data over sockets:

• writer would try to connect to a specified port, serializing points to a byte stream
• reader would start listening at a specified port, accepting any connections and decoding serialized points

This approach would enable connecting PDAL pipeline runs without a need to produce temporary files in between.

The idea is to be able to parallelize some processing on a single host, but thanks to sockets this could work also across different hosts.

[hobu]

serializing points to a byte stream

What does a serialized point byte stream look like? protobuf?

[wonder-sk]

What does a serialized point byte stream look like? protobuf?

For the start I thought about something less fancy... The question is whether the protocol would need to be stable between PDAL versions. If not, how about just dumping content of FixedPointTable's buffer as is? (plus point layout info when connection is established) That could also save some encoding/decoding work if either side is using stream mode...