BaseSet 1.0.0

• Now it is possible to list sets and elements that are not present in the relations but might be on the object via its factors: name_sets(), name_elements(), nElements() and nSets() gain a all argument.
• Fix a problem with $<- when the length did match a slot but the name didn't.
• Now it is possible to use sets and elements to subset a TidySet (but not for
  relations).
• New dimnames() and names() functions to discover the names of the data in
  the slots.
• Minor changes to getGAF() to improve speed.
• Increase R version dependency to 4.1 to remove magrittr dependency.