coreCollection - Core Collection

Create a custom sized Core Collection based on a distance matrix and applying the A-NE (accession nearest entry), E-NE (entry nearest entry) or E-E (entry entry) method as introduced in Jansen and van Hintum (2007) <doi:10.1007/s00122-006-0433-9> and further elaborated on in Odong, T.L. (2012) <https://edepot.wur.nl/212422>. Optionally a list of preselected accessions to be included into the core can be set. For each accession in the computed core, if available nearby accessions are retrievable that can be used as an alternative.