DA junctions must include roles emitter and base (and intrinsic, optionally)

[dalonsoa]

Problem

DA Junctions MUST have:

• 1 layer with emitter role
• 1 layer with base role
• 1 layer with intrinsic role (optional)
• Other layers

At the moment there is no enforcement of this, so when solcore tries to solve the problem, it fails.

Possible solution

When putting together the structure for solcore and before the junction is added to the structure here, there should be a check that the structure of the junction is indeed valid. This should be a separate function.

If that validation fails, the process should be interrupted and a pop-up window should inform the user of what is wrong with the structure.