Improve Gitlab-CI configuration and deploy Doxygen to EOSWEB
Changes to Gitlab-CI configuration:
- use shared (Docker based) runners, so that tests can be run from any fork
- build Doxygen documentation for master and tags
- deploy Doxygen documentation automatically to EOSWEB
This change requires the configuration of an EOS web site to deploy the documentation to.
As a side effect, I fixed a small bug in the top level Makefile
so that it's now possible to change the build directory location with an argument to make (e.g. make BUILDDIR=/tmp/build
).