[Proposal] Add warning message when setParam fails silently

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**Description**
While working on PEP8 cleanups in `netpyne/specs/netParams.py`, I noticed that `setParam` and similar methods fail silently when a label is not found.

**Current Behavior**
```python
if label in self:
d = self[label]
else:
return False # Silently fails, user is not notified
```

**Proposed Improvement**
I propose adding an explicit warning so users can debug their scripts easier:

```python
else:
print(f\"Warning: Label '{label}' not found. Parameter '{param}' not set.\")
return False
```

**Question**
Should I include this UX improvement as part of the PEP8 cleanup PR, or would you prefer a separate PR for this logic change?"

Start in netpyne/specs/netParams.py by reading setParam and the similar methods described in the issue. Confirm the intended behavior for a missing label, then verify that the warning is emitted and the method still returns False without setting the parameter.

Written by the indexing model from the issue text.