Allow user configurable number of initial table fields

When clicking on the "Create Table" button in the left nav, because I wasn't able to specify the number of fields to create, it will default to 2 fields.

This setting would be good as a configuration option. Something like $cfg['NumFieldsCreated'], or can be server based as $cfg['Servers'][$i]['num_fields_created'] (or whatever, name not important)

Then replace the hard-coded 2 on line 69 of /tbl_create.php with the entered option.