[fluidsystem][test] add forgotten fluidsystems to test, fix fluidsystems

What this MR does / why does DuMux need it: Adds forgotten fluidsystems to the fluidsystems-test.

This leads to small changes in the 3pimmiscible fluidsystem as well as some restructuring of the H2OHeavyOil fluidsystem. The H2OHeavyOil was adapted to match a 2c-fluidsystem which implements a binary diffusion coefficient. So far only the diffusion coefficient was implemented, but actually the binary diffusion coefficients without any changes were used. After discussion with @bernd we decided to move it to the binaryDiffusionCoefficient(), but for the sake of compatibility keep the diffusionCoefficient() which makes use of the new binaryDiffusionCoefficient().

Special note: I was not able to get the liquidphase2c running with the fluidsystems test, as it assumes a "constant"-component that gets values from the input file. The code compiles, but fails during execution because there is not input file. I have three possible solutions in mind, but maybe @bernd has a good idea:

1. Create a "unit"-component. This would be a (specialization of the) constant component where everything is set to "1". It would be similar to what we had with the default values in the constant component before.
2. Do not test the liquidphase2c fluidsystem
3. Paramters::init() was used to mimic an input-file