[Testing] Node groups evaluation & error handling

[aachman98]

Nodes

• [ ] Node group
• [ ] Loops: For, For-Each, For-Each Component
• [ ] If-Else Branch
• [x] Merge Objects
• [x] Create Objects
• [x] Import FBX/SVG
• [x] Duplicate Object
• [x] Custom Object/Curve
• [ ] Random Number
• [ ] Receive/Send to Sverchok

Evaluation modes

• [ ] first_time
• [ ] forced = False
• [ ] forced = True

Tests

• [x] Nested groups
• [ ] Recursive groups & infinite cyclic execution handling
• [x] Duplicate objects in groups
• [ ] Branched input evaluation in groups
• [x] Creating objects in groups
• [ ] Random number in groups & sub-groups (forced=True/False)