Fixed Float/Double SQL types

Fixed the Float/Double SQL type mix up. According to the scala documentation Float is a 32-bit floating number (SQL type float4) and Double is a 64-bit floating number (SQL type float8).

http://www.scala-lang.org/api/2.10.3/index.html#scala.Float
http://www.scala-lang.org/api/2.10.4/index.html#scala.Double