Add `src/.keep` files to `extra-source-files` in cabal files. Refs #65.

[ivanperez-keera]

Update extra-source-files in the cabal files of language libraries composed of auto-generated files only to include the src directory, so that the packages can be accepted in hackage, as prescribed in the solution proposed for #65 .

[ivanperez-keera]

Change Manager: Verified that:

• Solution is implemented:

  • [X] The code proposed compiles passes the tests. Details: Docker image:

    
    FROM ubuntu:trusty

  ENV DEBIAN_FRONTEND=noninteractive

  RUN apt-get update

  RUN apt-get install --yes software-properties-common RUN add-apt-repository ppa:hvr/ghc RUN apt-get update

  RUN apt-get install --yes ghc-8.6.5 cabal-install-2.4 RUN apt-get install --yes libz-dev

  ENV PATH=/opt/ghc/8.6.5/bin:/opt/cabal/2.4/bin:$PWD/.cabal-sandbox/bin:$PATH

  RUN cabal update RUN cabal v1-sandbox init RUN cabal v1-install alex happy RUN apt-get install --yes git

  We install the application first and then test it, in case any tests need to

  run the tool.

  CMD git clone $REPO && \ cd $NAME && \ git checkout $COMMIT && \ cd .. && \ cabal v1-install $NAME/$PAT/ --enable-tests && \ cabal v1-install $NAME/$PAT/ --enable-tests --run-tests -j1

  Command:
  ```sh
  $ docker run -e "REPO=https://github.com/NASA/ogma" -e "NAME=ogma" -e PAT="ogma-" -e "COMMIT=39851bc439c5e1ada82865be0d054dbe4736f741" -it ogma-test

  • [X] The solution proposed fixes the issues described. Details: Verified by manual inspection. The issue manifests mainly when uploading packages to hackage.
• [X] Implementation is documented. Details: No changes needed.
• [X] Change history is clear.
• [X] Commit messages are clear.
• [X] Changelogs are updated.
• [X] Examples are updated. Details: No examples affected.
• [X] Required version bumps are evaluated. Details: No bump needed (new file included, not used as part of code).