GUI-294: Various fixes based on UX feedback for Create Scaling Group wizard

Implemented in this pull request…

- Pushed the capacity label over so that the widgets all fit in a line.
- Fixed immediate validation error on membership page as soon as next is clicked.
- Merge the tags on to the general step and got rid of the tag step.
- Summary does not populate before visiting the associated step.
- Propagate mouseover now reads "Propagate to instances launched by this scaling group"

Notes w.r.t. validation error:
The immediate validation error is due to how Foundation validation works, which is form-based rather than step-based.  The workaround for the availability zones input is to pre-populate those, which isn't ideal but may work well for us here since it's trivial to remove an unwanted zone in a multi-select Chosen widget (--in fact it's easier to remove a zone than to add it, and it seems safe to include them all by default since there probably won't be more than a few, right?  Let's discuss if this is a concern.