New function to_json_ld to output features to json-ld

[anilbey]

Description

Adds a new function to output efel's features to JSON-LD format with annotations for the feature ids and the units.

Below is the classical output of eFEL extracted on 2 traces using 2 features.

[
        {
            "AHP_depth": np.array([26.998080940503804, 27.3636342342]),
            "AP_amplitude": np.array([72.0, 72.0]),
        },
        {
            "AHP_depth": np.array([56.3645747546, 55.142543543]),
            "AP_amplitude": np.array([74.2, 73.2]),
        },
]

It's corresponding json-ld output is the following.

{
  "@context": "https://bbp.neuroshapes.org",
  "data": [
    {
      "AHP_depth": [
        26.998080940503804,
        27.3636342342
      ],
      "AP_amplitude": [
        72.0,
        72.0
      ]
    },
    {
      "AHP_depth": [
        56.3645747546,
        55.142543543
      ],
      "AP_amplitude": [
        74.2,
        73.2
      ]
    }
  ],
  "AHP_depth": {
    "@id": "https://bbp.epfl.ch/ontologies/core/efeatures/AHP_depth",
    "unit": "https://neuroshapes.org/units/mV"
  },
  "AP_amplitude": {
    "@id": "https://bbp.epfl.ch/ontologies/core/efeatures/AP_amplitude",
    "unit": "https://neuroshapes.org/units/mV"
  }
}

Checklist:

• Unit tests are added to cover the changes (skip if not applicable).
• The changes are mentioned in the documentation (skip if not applicable).
• CHANGELOG file is updated (skip if not applicable).

[anilbey]

https://github.com/BlueBrain/bbp-ontologies/ has a more detailed mapping of efel features into the knowledge graph.