JSON update

[franzpoeschel]

Fix #1037, see there for a description.
This will probably not address all of the points noted therein, currently we have:

• capitalization. I favor capitalization-insensitivity, keeping consistent with how ADIOS2 does it.
• More lenient datatypes in ADIOS2: To users, it seems weird that they should specify adios2.engine.usesteps = true (as a boolean) but adios2.engine.parameters.OpenTimeoutSecs = "30" (as a string).
• Use TracingJSON everywhere: partially implemented, warnings not yet shown for global options
• Merge Two suggestions to fix CommonADIOS1IOHandlerImpl #1101 first
• This PR removes some keys from Dataset: chunks, compression and transform. So far, only transform was even implemented (I've replaced that implementation with a JSON-based one now), and only in ADIOS1 which is legacy anyway. For keeping compatibility with user code, we should maybe keep the fields for now, but deprecate them and remove all implementation surrounding them. Discussed: remove them fully in the API if we change the API contract (implementation) to break only once.
• Warn for global options: Dataset: unknown options should warn #1095
• Warning if file ending collides with JSON option
• Are these options in ADIOS2 capitalization insensitive? If not, I'll need to add some handling for that. Eh, let's not rely on this in ADIOS2. I've added exceptions for the lower case transformation now.

[franzpoeschel]

Warning for unused global options should work now, needs a bit more testing though. I configured an ADIOS2 dataset with the following string:

{
  "resizable": true,
  "asdf": "asdf",
  "adios2": {
    "unused": "dataset parameter",
    "dataset": {
      "unused": "too",
      "operators": [
        {
          "type": "blosc",
          "parameters": {
            "clevel": 3,
            "doshuffle": "BLOSC_BITSHUFFLE"
          }
        }
      ]
    },
    "hdf5": {
      "this": "should not warn"
    }
  }
}

Resulting warning:

Warning: parts of the JSON configuration for ADIOS2 dataset '/data/0/meshes/E/y' remain unused:
{"adios2":{"dataset":{"unused":"too"},"unused":"dataset parameter"},"asdf":"asdf"}

There is no warning for the HDF5 dataset as the HDF5 part is not parsed.

[franzpoeschel]

Only thing really still missing for finishing this PR is to introduce JSON configuration for stuff in ADIOS1 that has so far been configured via environment variables. Since this PR is already large enough, I'll suggest to postpone it to a follow-up.
Otherwise, I've split this thing into logical commits now, so reviewing by commit should be doable. I'll also go through things once again myself for a little cleanup, otherwise this is quite ready for review @ax3l :)

PS: What's also missing is to add JSON config to the MPI benchmarks. This PR removes the compression from them and doesn't replace them for now. Added that now

[franzpoeschel]

I've done some cleanup now and the CI is now also running fine

[ax3l]

I merged #1101 now :)

[ax3l]

Thanks a lot 🎉 Great work! 🚀 ✨