sql_type pattern check too limited; not very useful

[theage]

The regex for sql_type in generator/resources/xsd/database.xsd is of very limited use; it accepts nonsense like morse code .-..--. but rejects ENUMs with characters not listed in the regex.

I'd suggest to either drop this strict matching entirely, or to also accept any expressions of the form ENUM( 'quoted-value', ...).

This is a more generic description for the fixed #97 SqlType pattern brakes ENUMs with an "-" element.