Add the Ability to log multiple POTA references

[magicbug]

Discussed in #3096

^{Originally posted by nolith May 5, 2024}
POTA has the 2-fer, 3-fer location where a QSO is valid on multiple references. This is also supported by the ADIF spec but I was not able to mark a single QSO with more than one POTA reference. Am I doing something wrong or this is a missing feature?