Simulation configuration form

[bnmajor]

Two fixes to the PHOLD simulation config form:

1. Validation errors were never shown to the user. The form would be submitted but then be silently re-rendered on failure with no indication that there was an error or what the error was.
2. Field ranges weren't fully aligned with the actual PHOLD constraints
   1. lookahead had no upper bound
   2. There was no check that mean stayed greater than lookahead