When doing a group_by in a tree view, and then ordering by an
aggregated field which contains at least one capital letter in its name,
you will get an error and won't be able to ordery by this field.

Why? read_group is called when sorting a group by, which calls
_read_group_raw which then goes to call _read_group_prepare, which will
return order by terms in this manner ['id asc', 'x_Test desc']
the problem with this is that postgres automatically converts
non-quoted/non-qualified column name to lowercase, of course this means
that if we have a field "x_Test" but no field "x_test", it will try to
look up "x_test" instead of "x_Test" and since the column doesn't exist,
it will throw a ProgrammingError.

This commit changes this behavior by wrapping the order_by terms generated in
_read_group_prepare with double quotes, which postgres interprets
correctly.

Fixes #21348