global: Invenio 3.0 initial structure
- Prepares code structure for Invenio 3 and aligns package structure with current package standards.
- Removes all remaining legacy code from Invenio.
- Removes docker scripts temporarily from Invenio.
- Leaves current documentation in place.
Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>