This way children do not need to include the full header to get access to some utility functions for changing
the titles and icons of tabpages (and in fact do not need to know that there are tabs, could be something else)
OpenDatabase::createOpenDatabase now uses QException derived exception to report failure.
This makes it possible to catch the exception in a background thread and rethrow it when the Future is read.
Which makes it possible for the database window to properly report the problem.
Module can register action
Window adds this action to its menu
Clicking the menu item for the action has the expected result
But menu structure still needs work (everything is now put into one dropdown menu)
As a test implementation, this allows the TablesPage to open a CrudTab for a table/view without
the need for TablesPage, CrudTab and DatabaseWindow to know anything about each other.
in the direction of a plugin system.
DatabaseWindow now passes a Context to QueryTab and other pages that give those pages an
API for passing information up the system without knowing anything about the sytem.
