Add icons for new DataTypes.

We need 5 icons in total:

• one green icon nodeFaceSurface.png
• one green icon nodeEEGCap.png
• one yellow icon nodePSITable.png
• one yellow icon nodeNerfTable.png
• one yellow icon nodeSimulationState.png

As far as I remember, there is no need to add any CSS class for these images, we pass the image path to the jsTree library to render it.
The new icons need to be placed under folder tvb/interfaces/web/static/style/nodes

Details:
This is related to TVB-844 which added two new datatypes, PsiTable and NerfTable. These require icons for the datastructure/operations page. These datatypes fall in the Category 3: Adjacent Entities so color should be yellow.