Adds a publishable dockerfile (#4098)

        for Anaconda 3.4 and up - conda activate isis

        prior to Anaconda 3.4 - source activate isis

### Installation with Docker

The ISIS production Dockerfile automates the conda installation process above.

You can either build the Dockerfile yourself or use the

[usgsastro/isis](https://hub.docker.com/repository/docker/usgsastro/isis) 

image from DockerHub.

#### To build the Dockerfile

1. Download [the production Docker file](./docker/production.dockerfile)

2. Build the Dockerfile

  ```

  docker build -t isis -f production.dockerfile .

  ```

3. Run the Dockerfile

  ```

  docker run -it isis bash

  ```

#### Run run the prebuilt image

```

docker run -it usgsastro/isis bash

```

#### Usage with the ISIS data area

Usually you'll want to mount an external directory containing the ISIS data.

The data is not included in the Docker image.

```

docker run -v /my/data/dir:/opt/conda/data -v /my/testdata/dir:/opt/conda/testData -it usgsastro/isis bash

```

Then [download the data](#the-isis-data-area) into /my/data/dir to make it accessible inside your

container.

### Practical Usage with other conda packages

# vim: ft=dockerfile:

FROM usgsastro/miniconda3

RUN conda update conda && \

    conda install python=3.6 && \

    conda config --add channels conda-forge && \

    conda config --add channels usgs-astrogeology

RUN conda install -c usgs-astrogeology isis

RUN apt-get update && \

    apt-get install libgl1 -y && \

    rm -rf /var/lib/apt/lists/*

RUN bash -lc 'python "$CONDA_PREFIX/scripts/isisVarInit.py"'