Test Model column round-trips, fix FLOAT mapping
According to jdbc SQL standard java.sql.FLOAT is an alias for java.sql.DOUBLE and both should be mapped to scala.Double.
The single precision floating point type is java.sql.REAL, which is why we should map scala.Float to java.sql.REAL.
see http://docs.oracle.com/javase/1.5.0/docs/guide/jdbc/getstart/mapping.html#1055162

H2 seems to be the only one that maps FLOAT to Double though, but it fails the roundtrip.