Editable query results

Recently I rewrote the whole internal grid editing stuff to have bidirectional record sets. Means, editing grid data is no longer restricted to the Data tab. Any Query tab now allows you to edit your row data - at least if it's a simple query without joins and if it contains sufficient key columns. This was one of the most wanted features by users, described in issue #723.

As a side effect, query results are client-sortable now. When you click a column header, the grid itself is just sorted. This is surely not a replacement for having an ORDER BY clause in your query, but helps a lot to work quicker with simple grid results. Note that the Data tab works different here - the SELECT query is reposted with an adjusted ORDER BY clause. Only for the query tabs this is not possible as the query is totally user edited, no internal (and probably unsafe) SQL parsing is done.