DOC: Fix documentation of inheritance
The styling of the documentation of RecordType inheritance is broken: https://caosdb.indiscale.com/src/caosdb-server/specification/RecordType.html#inheritance, also there are a lot of FIXMEs and question marks in there.
Additionally, there is no documentation of how a Record inherits the properties of its RecordTypes and what happens, e.g., when it is lacking an obligatory property.
- Fixed styling and contents of RT inheritance
- Documentation in server API documentation (in-code javadoc)
- Added explanation on Records