The following changes have been made.

- `base-notebook`
  - `Changed`: Bump Ubuntu
  - `Changed`: Bump conda
  - `Fixed`: Add missing `apt-get clean`
- `minimal-notebook`
  - `Removed`: `jed` editor see #1174 (partial)
  - `Deprecated`: `emacs` editor (in the documentation and in the image) see #1174 (partial)
- `scipy-notebook`
  - `Fixed`: Add missing `apt-get clean`
  - `Changed`: Bump `dask`
  - `Changed`: Bump `protobuf`
- `r-notebook`
  - `Changed`: Bump `r-base`
  - `Changed`: Bump `r-rmarkdown`
  - `Removed`: The description of `tidyverse` packages because it's not the place to do that and it will always be obsolete.
- `datascience-notebook`
  - `Changed`: Bump `r-base` to `4.0.x` see #1102 (partial)
  - `Removed`: `plyr` package because it's retired fixes #1103
  - `Removed`: `r-reshape2` package because it's retired fixes #1103
  - `Changed`: Bump `r-rmarkdown`
  - `Changed`: Bump Julia
- `tensorflow-notebook`
  - `Changed`: Bump `tensorflow`
- `pyspark-notebook`
  - `Fixed`: Add missing `apt-get clean`
  - `Changed`: Bump `pyarrow`
- `all-spark-notebook`
  - `Fixed`: Add missing `apt-get clean`
  - `Changed`: Bump `r-base` to `4.0.x` see #1102 (partial)
  - `Changed`: Bump `r-sparklyr`

Run pre-commit hooks server side

nano -> nano-tiny

Fix bashate style issues

Fix python codestyle

Matplotlib test refactoring (Follow-on PR #1169)

Activate conda base environment by default

Stack update

Add `cm-super` package install to `scipy-notebook` required for `matplotlib` latex labels.

Some conda packages rely in the `conda activate` to set the corresponding environment variables, therefore just including the `bin` directory in the `PATH` is not sufficient.

Update Dockerfile fix spelling

- miniconda versions and arguments
- remove useless hd5 install (dependency of h5py)
- pin the version of pyarrow

Following images updated

- `base-notebook`
- `scipy-notebook`
- `tensorflow-notebook`
- `tensorflow`
- `datascience-notebook`
- `r-notebook`

Spark 3.0.1 -> fixes #1156

Added a note in the documentation to indicate that the build will only work with Spark current versions.

Added a note in the documentation to indicate that the build will only work with Spark current versions.

Changed `""` into `''` to pass an empty token. Seems to be linked to this warning:
```
/opt/conda/lib/python3.8/site-packages/traitlets/traitlets.py:2195: FutureWarning: Supporting extra quotes around Unicode is deprecated in traitlets 5.0. Use '' instead of "''" – or use CUnicode.
```

Added debug information (ouput of the command line).