Request: db_tools to have two additional functions, table list and column list

I think it would be great if we could get two extra functions in db_tools.

One for listing all the tables in the database. I know this already exists in includes/functions_install.php, but would be better in db_tools IMO. I would also remove it from the 3.2.x functions_install.php, but not from 3.0.x to prevent breaking things with other mods that use it from there.

One for listing all the columns in a table. The functionality is almost already there in db_tools in the sql_column_exists function. You'd just have to move the queries to a separate function and then could use that function in the sql_column_exists function.