groupMembersReturn: Forms return list of groupAddAssign function
In rmsharp/nprcmanager: Genetic Tools for Colony Management

@return A list with members savedGroupMembers, savedScore, and if withKin == TRUE groupKin as well.

1	groupMembersReturn(savedGroupMembers, savedScore, withKin, kmat)

`savedGroupMembers`	selected animal group
`savedScore`	score of selected group, which is the group having the largest minimum group size
`withKin`	logical variable indicating to return kinship coefficients when `TRUE`.
`kmat`	numeric matrix of pairwise kinship values. Rows and columns are named with animal IDs.