Make "Create Kubernetes cluster" form submit active by default

Currently, we disable the form submission until all required fields are filled out:

Screen_Shot_2018-05-15_at_11.07.29_AM

Instead, we can improve the experience by making the submit button active by default and including validations for when a user tries to submit the form without all required fields. This gives feedback to the user quickly and doesn't leave them guessing as to why they are unable to submit the form.

Related: This comes from Sid's demo where he didn't understand why a button was disabled initially (in a different scenario).

This also copied the paradigm we use on the register page:

img