Update install doc and readme with info on optional deps

README.md

@@ -8,13 +8,20 @@ Data Model.
 
 ## Install
 
-Install steps are described in the documentation generated from `/docs/source/installing.rst`.
+Simply install IMAS-Python with ``pip``:
+```bash
+pip install imas-python
+```
+or with optional dependencies for netCDF and xarray support:
+```bash
+pip install imas-python[netcdf,xarray]
+```
 
-Documentation is autogenerated from the source using [Sphinx](http://sphinx-doc.org/)
+More details are described in the documentation generated from `/docs/source/installing.rst`.
+The documentation is autogenerated from the source using [Sphinx](http://sphinx-doc.org/)
 and can be found at the [readthedocs](https://imas-python.readthedocs.io/en/latest/)
 
-The documentation can be manually generated by installing sphinx and running:
-
+To generated the documentation yourself, install the ``docs`` optional dependencies and do:
 ```bash
 make -C docs html
 ```

docs/source/installing.rst

@@ -13,6 +13,28 @@ To get started, you can install it from `pypi.org <https://pypi.org/project/imas
 
     pip install imas-python
 
+You can also install optional dependencies (e.g. netCDF and xarray):
+
+.. code-block:: bash
+
+    pip install imas-python[netcdf,xarray]
+
+
+List of optional dependencies
+-----------------------------
+
+- ``netcdf``: enables storing/loading of IDS to/from netCDF files
+- ``xarray``: enables loading IDS (entire IDS or part of it) into an xarray ``dataset``
+- ``h5py``: enables ``analyze-db`` CLI option 
+- ``docs``: installs required packages to build the Sphinx documentation
+- ``test``: installs required packages to run the tests with ``pytest`` and ``asv``
+
+.. note::
+
+    Some tests will be skipped unless you also have ``imas_core`` installed
+    (it is not yet available on PyPI, so you will need to install it from sources
+    if you have access to them at https://git.iter.org/projects/IMAS/repos/al-core) 
+
 
 Local installation from sources
 -------------------------------