Implement missing CAPI methods

[schmoelder]

Since PR #59 was closed prematurely, this is a continuation.

Original description:
Adds a simple C interface to libcadet. The parameter provider interface
is realized by callback functions. A simulation can be performed and
the solution at the outlet of the unit operations can be queried.

Also includes a test application that dynamically loads the library at
runtime (only Windows) and executes a simulation specified in JSON
format internally.

This commit provides the first steps regarding #16 and, thus, #12.

To do:

• Inlet
• Outlet
• Bulk
• Particle
• Solid
• Flux
• Volume
• InletDot
• OutletDot
• BulkDot
• ParticleDot
• SolidDot
• FluxDot
• VolumeDot
• InletSens
• OutletSens
• BulkSens
• ParticleSens
• SolidSens
• FluxSens
• InletDotSens
• OutletDotSens
• BulkDotSens
• ParticleDotSens
• SolidDotSens
• FluxDotSens
• VolumeDotSens
• LastState
• LastStateTimeDot
• LastUnitState
• LastUnitStateDot
• LastSensitivityState
• LastSensitivityStateDot
• LastSensitivityUnitState
• LastSensitivityUnitStateDot
• Coordinates
• SolutionTimes
• getNumUnits
• Simulation runtime (/meta/time_sim)
• /meta/file_format

---

Moreover, some things are still unclear / inconsitent and will be addressed later, see #283

[schmoelder]

We implemented most of the methods but still need to test them (which we will do in tomorrow's Dev-Call). The reason why the test suite fails is probably because of the following:

https://github.com/modsim/CADET/blob/master/test/testCAPIv1.cpp#L3

So we need to modify the tests to make them OS independent.

[jbreue16]

The file format is hardcoded in both the driver.hpp where the meta output is written and now also hardcoded (with value 040000) for the CAPI.

[schmoelder]

I don't understand the build issue with MacOS. If you have time, could you please have a look @sleweke?

[schmoelder]

This PR is ready to be reviewed! 🥳

We test all unit operations using createLWE with different combinations of solution recorders (i.e. split_components=True/False etc) in CADET-Python and check that the simulation outputs have the correct shape. We could also consider adding such test in test/testCAPIv1.cpp but for now, it seems "good enough" to me. @jbreue16 and I also had some discussions about the parametrization of tests and that for system tests, we could also consider writing Python scrips as they are much easier to maintain and extend. If I'm not mistaken, that's also something he does for the convergence tests.

[jbreue16]

The MacOS build has been fixed, and all tests have successfully passed. Dimensionality of outputs has been thoroughly tested by @schmoelder.

All necessary changes for v5 have been implemented. Any outstanding issues are documented in #283.