AngularJS: improvements of wizard steps

include:
- async caching of html partials
- spec fixes
- bug fixes
- transition from wizard to overview

Change-Id: I64317aebd5f6d3d0a33a849ce82f06f5c0d393eb
Reviewed-on: http://review.couchbase.org/38738
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>