Add validation for sensor

[VaibhavPage]

Is your feature request related to a problem? Please describe.
Currently there is no validation for sensors other than checking that each signal type is supported.

Describe the solution you'd like
we need to add validation for the following rules:

• each signal only defines one of: (stream, artifact, calendar, resource, webhook)
• all resource object trigger parameters reference a signal that's defined
• all signal time filters specify a start time before stop time and a stop time after current time (allow nil values here to represent +/- infinity?)
• calendar signals all have either a schedule or interval defined and the recurrence patterns are okay