Version 1.5.0 with many improvements

This is an upgrade release with lots of UI and documentation improvements and various bug fixes. It includes a pre-built binary for Linux and sources which should build for Windows and Macintosh. Volunteers to test build on those platforms would be welcome.

New features since v1.4.0svn include a button to delete the records found by a Query Builder query, some useful context menu items in the data viewer, a button to extract the SQL code generated by the Query Builder, and a Find Dialog which allows searching for rows in a table: this differs from running a query in that the found rows are editable.