talk about special features in use-case (#413)

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Co-authored-by: Jaquier Aurélien Tristan <aurelien.jaquier@epfl.ch>

README.md

@@ -139,6 +139,8 @@ To get a list with all the available feature names
 efel.get_feature_names()
 ```
 
+Note that the extra-cellular features, the bpap_attenuation feature and the check_ais_initiation feature are not listed above because they have to be used in a special way, as described [here](https://github.com/BlueBrain/eFEL/blob/master/examples/extracellular/extrafeats_example.ipynb) for extra-cellular features, [here](https://github.com/BlueBrain/eFEL/blob/master/docs/source/eFeatures.rst#bpap_attenuation) for bpap_attenuation feature and [here](https://github.com/BlueBrain/eFEL/blob/master/docs/source/eFeatures.rst#check_ais_initiation) for check_ais_initiation feature.
+
 To change the spike detection threshold setting (default is -20 mV)
 
 ```python

docs/source/python_example1.rst

@@ -9,11 +9,14 @@ To get a list with all the available eFeature names::
 
     efel.get_feature_names()
 
+Note that the extra-cellular features, the bpap_attenuation feature and the check_ais_initiation feature are not listed above because they have to be used in a special way,
+as described `here <https://github.com/BlueBrain/eFEL/blob/master/examples/extracellular/extrafeats_example.ipynb>`__ for extra-cellular features, `here <https://github.com/BlueBrain/eFEL/blob/master/docs/source/eFeatures.rst#bpap_attenuation>`__ for bpap_attenuation feature and `here <https://github.com/BlueBrain/eFEL/blob/master/docs/source/eFeatures.rst#check_ais_initiation>`__ for check_ais_initiation feature.
+
 The python function to extract eFeatures is get_feature_values(...).
 Below is a short example on how to use this function.
 
 The code and example trace are available
-`here <https://github.com/BlueBrain/eFEL/blob/master/examples/basic/basic_example1.py>`_::
+`here <https://github.com/BlueBrain/eFEL/blob/master/examples/basic/basic_example1.py>`__::
 
     """Basic example 1 for eFEL"""