Add support for associating input formats with streams from psql

[pipelinedb]

No description provided.

[pipelinedb]

CREATE TYPE ... might actually be better for this.

http://www.postgresql.org/docs/9.2/static/sql-createtype.html

[pipelinedb]

Or we could just have a pipelinedb "catalogue" table that maps an input format to a stream.

[pipelinedb]

CREATE STREAM stream (
id INTEGER
data TEXT) WITH DECODER DELIMITED(',');

REGISTER DECODER custom_decoder (
    binary = 'some/path'
);

CREATE STREAM events (
id INTEGER
data TEXT) WITH DECODER custom_decoder