RecuMergeStruct(A, B)

RECUMERGESTRUCT recursively merges fields & subfields of structs A and B
The aim is to produce 1D arrays of every shared field in the structs, indexed by the struct identifier, which we assume is a point field somewhere at the top level. Scalars are aggregated to vectors, vectors are aggregated if of equal size, mxn matrices are placed in cell arrays, as are cells and char arrays.