Add scheduled image builds for improved security

[poikilotherm]

Images should be updated regularly when the base image (currently CentOS) is updated.

Linked builds on Docker Hub only work for non-official images (they might have a lack of resources...), so we need to add this ourselfs.

First idea: use Travis CI, they offer scheduled builds OOB.

[pdurbin]

You might want to investigate using https://jenkins.dataverse.org which is a new resource that will be documented in IQSS/dataverse#5725

If you'd like some jobs to be added, I would suggest opening issues at https://github.com/IQSS/dataverse-jenkins/issues

[poikilotherm]

This should include a regular security scan when building the images.

This can be done using Clair as standalone, Anchore or similar. See also blog post on different engines part 1 and part 2.

Anchore seems benefical as it also offers scanning for Java libs etc.