Add Voronota SASA energy term

[mlund]

Now that we have internal access to Voronota-LT, we can use it to calculate SASA to capture hydrophobic and ion-specific interactions.

• [ ] Add energy term in energy.h
• [ ] Add test. This could be based on existing tests where other SASA energy is used.
• [ ] Investigate if existing SASA energy code can be reused.