[Feature Request] Output all nodes from canvas flow

[ahariharan95]

Currently, only one output node (that was executed) and it's input nodes are being output when a model is exported. Would it be possible to have all nodes in the flow be output?

[laurachiticariu]

Here's a design for this issue:

1. The edit panel of each node (except the Input document node) should have a checkbox Output this node
2. If the checkbox is checked, the behavior for the export function should be to include the .xml file for this node (and all its inputs) into the exported package, and add the node name to the list of outputTypes in manifest.json.

We should also discuss the behavior of the Run button. Sometimes it is useful to run multiple nodes from the canvas. So the front end could be enhanced to allow selection of a set of nodes (Run would output all selected nodes) or selection of all nodes (CTRL+A to run all nodes).