Install Composer dependencies for Docker + add .dockerignore

[osma]

This PR contains the changes from @jrvosse's PR #1157, i.e. Composer dependencies are now installed within the Docker container.

I'm still a bit nervous about the interaction between changes done on source tree and the Docker image. I thought it would be better to have a cleaner separation between them - for example, whatever is (or isn't) done with Composer on the original source tree shouldn't affect how Composer packages are installed within the container.

So in an additional commit, I created a simple .dockerfile (based on .gitignore) that omits the following files and directories when copying files inside the Docker container:

config.ttl
build
vendor
report
components
plugins/*
composer.phar
composer.lock
tests/jena-fuseki*
.vagrant
.project
.DS_Store
.phpunit.result.cache

Not sure if this is the exact set we want but I think this is a good starting point, and it seems to work. These are files and directories that are not under version control anyway, and with Composer running inside the container, building a Docker image from a fresh git clone-d source tree already works (I just tested it), so I don't think there should be any danger in excluding these files. As a bonus, potentially large files such as Fuseki installations used by the test suite are excluded from the Docker image as well.

Comments @jrvosse @kinow ?

[codecov]

Codecov Report

Merging #1162 (a6c8837) into master (4a050f4) will not change coverage.
The diff coverage is n/a.

❗ Current head a6c8837 differs from pull request most recent head 046169b. Consider uploading reports for the commit 046169b to get more accurate results

@@            Coverage Diff            @@
##             master    #1162   +/-   ##
=========================================
  Coverage     67.97%   67.97%           
  Complexity     1584     1584           
=========================================
  Files            32       32           
  Lines          3888     3888           
=========================================
  Hits           2643     2643           
  Misses         1245     1245           

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[kinow]

👍 completely forgot about the .dockerignore, sorry @osma.

It doesn't hurt to add a few extra files for just-in-case too, if you'd like. Last one I remember writing I added .git, .ssh, and other files that were not supposed to be included in the Docker build context.

[sonarcloud]

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[osma]

Thanks for the tips @kinow, I added .git as well which makes a lot of sense and should make the Docker image a lot smaller. I can't think of why .ssh would be there in the source tree in the first place, and the others in your example file were at least for the most part related to Python tooling, so probably not relevant for a PHP project.

I think I'll merge this with this set. We can always add more entries to .dockerignore later if necessary.