fix snowflake seed types, add chunking for seed files with more than 16k rows

[cmcarthur]

This fixes two things:

• It allows seed files over 16k rows on Snowflake
• It uses floats for seed files instead of numeric / decimal types

[cmcarthur]

Fix for #690

[drewbanin]

@cmcarthur is this correct? It seems to me that the second chunk would get the bindings from the first chunk?

[cmcarthur]

bindings is reset inside the outer loop

[drewbanin]

LGMT @cmcarthur

let's get this working in development, then revisit the float8 decision :)