Specify entropy model's adiabatic profile via function

[RanpengLi]

The chemical compositions and component's entropies can also be specified by a function. Each components will be equiliabrated using the multi-component entropy method.

For all pull requests:

• I have followed the instructions for indenting my code.

For new features/models or changes of existing features:

• I have tested my new feature locally to ensure it is correct.
• I have created a testcase for the new feature/benchmark in the tests/ directory.
• I have added a changelog entry in the doc/modules/changes directory that will inform other users of my change.

[gassmoeller]

Hi @RanpengLi, apologies this will have to wait a bit longer before I can look at it. Until then you can already:

• Find out why the indent tester fails
• Add a test case that uses the new feature
• Add a changelog entry that described what the new feature is for