Add she::Display::setMousePosition()
Use IntersectClip when possible
Fix ToolBar behavior to avoid changing tools unintentionally

- Avoid opening other groups if the user is not with the mouse down
- A second MouseUp closes the group
Add DEBUG_PAINT_EVENTS to manager.cpp
Fix call to update_mouse_position() when Allegro mouse position is used
Minor changes in Window::moveWindow()
Minor changes in Widget::scrollRegion()
Translate Widget::m_updateRegion field when the widget is moved
Fix Editor scroll issues: we cannot process several WM_MOUSEMOVE in one UI loop-cycle

We have to wait to validate not-scrolled regions before we can use
Widget::scrollRegion() or Window::moveWindow() again. This is an issue
to see in the future (to avoid lossing mouse move messages). At the moment,
one solution is to use the last received mouse move message.
Make IntersectClip non-copyable
Add "Lock Alpha" ink (issue #155)