Adding support for NSUUID handler for any guid/uuid formed string

Adding NSUUID conversion on executeUpdate and executeQuery on FMDatabase and uuidForColumn and uuidForColumnIndex on FMResultSet.

This is useful when the string data in the columns are guid-form. Most of my projects are using guid/uuid as primary keys which is not supported in sqlite and doing conversion back and forth between NSUUID and NSString is error-prone (since string data usually case sensitive which make equal uuid unequal just because they are written in different case).