Input validation for gossip graphs

[RamonMeffert]

• [x] The identity relation for N and S should always be satisfied
  • either Flag input as incorrect w/ error;
  • 😕 bad ux
  • 😃 easy
  • or Give a warning and add implied identity relations.
  • 😃 good ux
  • 😕 might be unclear to some users
• [x] Input should be in correct format
  • [ ] Numeric (03-20-123 0-1-2-3) or alphabetic (Abc ABC abC)
  • [ ] Different separators
  • [ ] either always allow multiple (possibly arbitrary) separators in input, and give a warning when more than one is used
    • 😃 good ux
    • 😕 how would number input work, as it needs 2 different separators?
  • [x] or reject input when separators are inconsistent
    • 😕 bad ux
    • 😃 easy
• [ ] Input should not contain unconnected nodes (?)
  • [ ] If no one can reach a node, it will never be included in any ca

[RamonMeffert]

Most of this is included in #29

[RamonMeffert]

The most important parts of this are done, the other issues are addressed in #15 and #16 (and possibly #21) so I'm closing this