indirect access to DDLCompiler.get_column_specification via overrideable construct schema.CreateColumn

[Mike Bayer]

so that @compiles(CreateColumn) can be used for things like this:

CREATE TABLE mytable (
  id INTEGER,
  foo SPECIAL DIRECTIVE XYZ
)

this is an optional for 0.8 thing.

[Mike Bayer]

a patch is attached, however some better system of injecting the custom CreateColumn elements into the CreateTable should be devised. People are going to want this to work automatically for certain types of columns. So think about this more.

[Mike Bayer]

1c325dc9c73820e78ab79d4aa160dc0f6cbe3b65

[Mike Bayer]

Removing milestone: 0.8.0b1 (automated comment)