Straighten out profile ordering semantics

Here's what I think works best:

* Any profile in the Environment before application.yml
is processed takes precedence (i.e. it will be last in the
list of active profiles in the live app)

* Any profile in the Environment before SpringApplication
starts takes precedence (so any added on the command line or
with System properties come after ones added using
the SpringApplication API)

* The order of profiles in application.yml is irrelevant -
profiles are applied in the order they come out of
Environment.getActiveProfiles()

Fixes gh-342