Molgenis-py-bbmri-eric

- Adds step to fill combined_network field
- Fix issue 61, import of NL data fails due to self-referencing columns

- PIDs are prefixed with `1.` (example: `1.6ed7-328b-2793`)

- The PID feature can be turned off completely by supplying a NoOpPidService

- PID URLs are based on a config parameter instead of the session

- Change PID format to use a random 12 digit hexadecimal number (example: `6ed7-328b-2793`)
- Introduced a DummyPidService to test publishing without interacting with a Handle server
- Fixed issue 35 References to EU networks and persons don't pass validation
- Fixed issue 41 Rows of node EU are overwritten by other nodes that reference them

- Persistent Identifiers (PIDs) for biobanks
- New biobanks are automatically assigned a PID
- Biobank name changes are reflected in its PID record
- Removal of a biobank is reflected in its PID record
- Removed command-line "eric" command
- Fixed issue 42 ID validation should not allow and .
- Fixed issue 43 Current ID validation results in false-positive invalid IDs