remove_RLum() ... add methods + generic

[RLumSK]

We can already filter RLum-class objects and lists of such object using get_RLum(). To facilitate a better workflow, it would be good to have an remove_RLum() function.

• Internally we make a dispatch and generate a get_RLum() call that gets executed.

Example

object_sel <- remove_RLum(object, recordType = "IRSL")