MainWindow: Increase default size, tabify docks by default

Increase the default size of the main window a bit.

Move the SQL log dock to the right side and tabify it with the plot
dock. This way there is much more space for actual information by
default.

The idea behind both changes is to make it easier for first time users
to find their way around and offer them a more appropriate window layout
for the usual tasks. The layout is still entirely configurable and
non-first-time users are not affected at all.