[WIP] Clean up entity patching code

Done:

* split patching code from Entity and derivatives
* drop usage of deprecated term related methods defined by Entity
* split Fingerprint patching code into its own class

TODO:

* fully replicate the old tests and then remove them from EntityTest and derivatives
* drop usage of deprecated claim related methods defined by Entity
* drop usage of deprecated Item methods
* split Statement patching code into its own class
Or not. Added in 186fbd7e7ef86505d4bc309fd9f82ca91ef4a373, so guess @WMDE-Fisch does not have his IDE set to tabs. Heresy! :)