Differentiate vdw and ionic radii in the UI

[rlavendomme]

Current status

In the current development version 4403faf MoloVol can recognize ionic species and use the corresponding ionic radius instead of vdw radius.
For undefined oxidation states (charges) in the elements.txt file, MoloVol will automatically pick the vdw radius instead.

Issue

Users are not warned when the vdw radius is used for an ion of undefined oxidation state. Therefore, they could proceed mistakenly thinking that an ionic radius is used.

Proposed change

Use color codes in the element table of the UI.
One color could be used for neutral element symbols and vdw radii, and a second color for charged element symbols and ionic radii.
Currently red, cyan and grey are already used to indicate null radius, manually entered radius, and excluded element, respectively.
We could use light apple green and yellow for vdw and ionic symbols/radii, for example.

Improvement

Such a feature would clarify what element data is used by the program for calculation.