Dialog: Make draggable

[FlowIT-JIT]

Make dialog draggable to allow user to reveal content behind it.

Proof of concept:

d = new Fit.Controls.Dialog();
d.Modal(true);
d.Title("Editor output");
d.Width(80, "%");
d.Height(200);
d.Dismissible(true, true);
d.GetContentDomElement().innerHTML = input.Value();
d.Open();

dr = new Fit.DragDrop.Draggable(d.GetDomElement(), d.GetDomElement().querySelector("div.FitUiControlDialogTitle"));

It works as long as one drags it around. Releasing the mouse button causes it to return to the center of the screen. The reason for this can be found here: https://github.com/Jemt/Fit.UI/blob/4344573b10652b501babe4b65cda5480ba37fe1c/Controls/Dialog/Dialog.js#L932

An observer and various functions are responsible for ensuring the dialog remains centered when the size of the content within the dialog changes, which in turn may cause the dialog to change size. Obviously we just need to disable this mechanism the moment the user drags the dialog around for the first time.

[Mhbuur]

+1 This is a great suggestion! My company may be able to fund further development, lets get in touch.

[FlowIT-JIT]

Fixed with commit https://github.com/Jemt/Fit.UI/commit/223fc46148d08fe9309ec3370386c4c63cbe8059