List for marked nodes

To allow connecting faraway nodes which cannot be shown on the same focus+context view, we need to allow marking of those nodes.

Benja had already developed a list for marked nodes into GZZ client, but after abandoning GZZ this feature was kind of lost. Of course, this will be a feature of full working Loom, but this would also be useful in Fenfire's MindMap (later MM) applitude.

MM has a 2D structure view, where marked node list could work as it worked in GZZ: marked nodes can be connected to accursed node.

In MM nodes created in 2D structure view must also be able to place on 2D canvases. When on 2D canvas view, marked nodes in list should be able to drag & drop onto canvas.

New features:

• nodes can be dragged & dropped onto 2D canvas
  • in MM this will cause a connection between marked node and paper node representing that canvas, also dropping coordinates are added into connection