Added simple url conflict checks, refs #1878

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | ---
| Fixed tickets | ---
| Refs tickets  | #1878
| License       | MIT
| Doc PR        | ---
did the api change for the FormLib? I thought the name had to be `handleCommand`? (but admittedly, I really dislike FormLib)