Fix the issue about number of inputs/outputs in experiment editor

Summary

This issue was a broader issue related to the numbering of inputs/outputs in the IOMapping of the experiment editor. The inputs/outputs layout can contain multiple elements such as label or object from a list in a specific row.

Tricking this by substracting -1 to the number of elements only works when the number of input/output is 1. However from row 2 and later the number of elements per row (2) gets multiplied by the number of rows and the bug lies around that calculation.

Only looking at the number of rows (containing a single input or output) gives us the correct number of inputs and outputs.

Relevant issue(s) fixed

Fixes #257 (closed)