update data types from NUMERIC to DOUBLE_PRECISION

[Ludee]

We will change data types from NUMERIC and DECIMAL to DOUBLE_PRECISION
openego/data_processing#72
ego.io has to be updated as well.

I'm not sure how to handle FLOAT. Any idea? @gplssm @nesnoj

[nesnoj]

FLOAT is a postgreSQL-specific type. The docs say

PostgreSQL also supports the SQL-standard notations float and float(p) for specifying inexact numeric types. Here, p specifies the minimum acceptable precision in binary digits. PostgreSQL accepts float(1) to float(24) as selecting the real type, while float(25) to float(53) select double precision. Values of p outside the allowed range draw an error. float with no precision specified is taken to mean double precision.

So you can simply replace FLOAT by DOUBLE PRECISION in dp as there're no occurences with specified precision.

[nesnoj]

Approved in #30: No NUMERIC left (except in model_draft).