Possible improvements for the image

[typoworx-de]

I've tested some possible improvements:

1. ability to change document-root in docker-container
2. fix permissions which may be screwed on first-start of project for fileadmin,typo3conf,uploads
3. ability to use docker-entrypoint.d folder with custom scripts for startup (f.e. typo3-cli, migrations, ....)

https://github.com/martin-helmich/docker-typo3/pull/248/files

[fogshot]

+1 for the permission issues