Issue title: Make "Dev" Default Environment When Creating/Pulling/Pushing a Site
 Issue body: Feature/Enhancement Request
===========================

**User Story**

As a Kalabox user who creates sites often and doesn't always read the form, it'd save me time for the default environment to be "Dev", since many of my sites I create (or push to) don't have multi-dev environments.

**Solution**

Make "Dev" the default environment on these forms.
 Comments: 
 Comment 0: 👍 
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