Refactor Plausi from musdb to move the logic into this subrepository

See #948

README.md

@@ -1,3 +1,22 @@
 # Quality Assessment Tools at museum-digital
 
-The classes of this library provide tools to access the quality of museum object records and provide tips for improving it.
+The classes of this library provide tools to access the quality of museum object
+records and provide tips for improving it.
+
+## Tools
+
+- PuQI
+
+PuQI (class `MDPuqi`) generates a score determining the quality of object metadata
+based on e.g. counting linked entries.
+
+## Plausi
+
+Plausi analyzes an object's linked events (e.g. production, use) and identifies
+logical inconsistencies.
+
+## Publications
+
+### PuQI
+
+Rohde-Enslin, S. (2015). PuQI – A Smart Way to Create Better Data. Uncommon Culture, 6(2), 122-129. <https://uncommonculture.org/ojs/index.php/UC/article/view/6218>