Fixed decimal/float length and precision for db.xml files

Missing some more backwards compatability in the Legacy xml parser. Added proper functionality for Decimals (tested on atNumber) and I think it will also correct for Floats (but untested).

Also, doctrine does NOT support changing the display length on integer type columns (at least nothing I could find in their docs and setting the precision or length doesn't seem to make a difference in the addColumn options), and there are quite a few type="I" size="1" columns in the database. Just thought I'd mention it probably wouldn't hurt to clean these up to be the proper size integers at some point. An example of something that would be different in this aspect would be the atAddressSettings.akHasCustomCountries field.