Support new QE7.1 keywords and DFT+U specification in Nexus

**Is your feature request related to a problem? Please describe.**

QE7.1 changed how DFT+U is specified. This requires updates to Nexus to use and some strategy devised for use of older and newer versions.

**Describe the solution you'd like**

One including an error trap of mismatched options and versions, or an automatic upconversion if the implementations are compatible.

**Describe alternatives you've considered**
None

**Additional context**

Would be ideal for next release but analysis needs to be done on how much work this is.