These two columns let recommend an order, respectively, for tables in their
schema, and columns in their table.
In addition of these new columns, "arraysize" has been also added.
All these new columns are already supported when creating a TAP_SCHEMA from
an XML file.

[TAP] Add an XML TableSet parser. The main modification done in JDBCConnection is about the schema prefix of table when the DBMS does not support schemas: now, only standard tables are expected with the prefix 'TAP_SCHEMA_' and the upload tables also with 'TAP_UPLOAD_'.