Add option to copy-drag nodes

[juzzlin]

• Could be a checkbox on the toolbar
• When enabled, the parent node will be copied instead of creating new

[juzzlin]

Fixed in e8d7b65

[l3td33r]

I think text shouldn't be inherited? Makes it harder to edit the new node. Inheriting color is cool tho.

[juzzlin]

It is like this by design, but indeed this could be a setting.