Show error for author when create option with invalid flags

[shadowspawn]

The option parsing is quite loose. This means authors do not get feedback they are using unsupported flags when creating options.

In particular could throw an error for:

• more than two flags
  • #1862
  • #2222)
• short flag with more than 1 character
  • #1718
  • #2227
  • #2211