Window-tool: option to use corner (glass-glass) using monorail sliding window.

[mbriers]

Give the option to create this setup with only the window tool. (glas on glas corner option while using a monorail sliding window)

Stept to model it for now: (see attachments)

- create window with a open frame

- create sliding door behind the open frame

- create mesh or beam for frame sliding door.