Ricgraph

The following improvements have been made to Ricgraph.

Ricgraph:
- Added a parameter "--organization" to some harvest scripts, so that they can be used for harvesting data from different organizations.
- Added a parameter "--empty_ricgraph" to the harvest scripts, to indicate whether Ricgraph should be emptied or not.
- Modified the initialization file ricgraph.ini-sample. You will need to copy this file to ricgraph.ini and fill in your own (organization) values. Some keys have an "organization abbreviation", which can be passed to the parameter "--organization" of a harvest script, or which can be filled in when running a script.
- Added a batch script to to run a number of harvest scripts after each other.

Documentation:
- Added a comparison of Ricgraph to other systems, such as Lens, OpenAire Graph and OpenAlex.
- Modified documentation to explain how to harvest data from different organizations.

The following improvements have been made to Ricgraph.

Ricgraph:
- Modified the initialization file _ricgraph.ini-sample_ (to be copied to _ricgraph.ini_). Now it has parameters that contain the node properties. You will need to update your _ricgraph.ini_ file with these parameters.
- Added scripts to export _person_ nodes to a csv file. These can be found in directory _export_ricgraph_examples_.

The following improvements have been made to Ricgraph.

Ricgraph:
- Ricgraph now has new fields in a node: a field for a year and a field that holds the name(s) of the source(s) a node has been harvested from.
- Videos have been added to illustrate the workings of Ricgraph and Ricgraph explorer.
- The documentation has been updated.

Harvesting:
- Each harvest script has been modified to be able to use the new fields for year and harvesting source.

The following improvements have been made to Ricgraph:

Ricgraph:
- Rewrite of the function to connect two nodes.
- Added function to merge two 'person-root' nodes (needs some improvement).
- Added parameter RICGRAPH_NODEADD_MODE which controls how nodes are added to Ricgraph (see documentation in file docs/ricgraph_install_configure.md).
- Improved documentation.
- Added a Ricgraph logo.

Harvesting:
- Added a harvester for [Utrecht University staff pages](https://www.uu.nl/medewerkers).
- Added a harvester for [OpenAlex](https://openalex.org).
- Improved harvesters for Pure, Yoda-DataCite and Research Software Directory.

The following improvements have been made:
- Added faceted navigation to Ricgraph explorer.
- Improved user interface for Ricgraph explorer.
- Added a cache in function read_node() in ricgraph.py so nodes read from the graph database are stored in that cache. That will prevent a number of search operations in the graph database, making ricgraph faster.
- Improved efficiency (more speed, less memory) of Pure harvester.

A number of improvements. The following features have been added:

- Ricgraph has been extended with functions to get neighbors of nodes;
- Ricgraph explorer has been extended to allow search on substrings and sorting by clicking on a table header.