Solve issue with assigning inputs/outputs in a Jupyter cell

[StefanVriend]

The code analyser in the NaaVRE recognises per cell which declarations are inputs and which are outputs. Cell inputs and outputs are required to link cells (or building blocks, if you will) through the Experiment Manager (i.e., a workflow builder). Currently the code analyser has a hard time interpreting R syntax; it's overly sensitive in assigning variables as inputs. To make our workflow run in the NaaVRE, this should be solved.

Gabriel and Spiros will tackle this issue.

[CherineJ]

Shortcut

Updates in the VRE make it now possible to specify the inputs, outputs and dependencies of a cell through a commented header section. In this header it can also directly be specified of which type the inputs and outputs are, so that this does not need to be done in the code analyser. This is however only a temporary solution and in the long run the code analyser should be smart enough to detect inputs and output of a cell correctly on its own.