Refactoring, Dynamic prefix and AWS v2 (extended)

[nevins-b]

This is a continuation of @ph's awesome work in #102

This takes into account most of the logic and grammatical changes mentioned in the review of that pull request. It does not do the renaming or deprecation of options.

[ph]

@nevins-b Can you sign the CLA?

Would you mind doing step 2 of the contributing guide? https://github.com/elasticsearch/logstash/blob/master/CONTRIBUTING.md#contribution-steps

[nevins-b]

@ph Should be all set.

[karmi]

Hi @nevins-b, we have found your signature in our records, but it seems like you have signed with a different e-mail than the one used in yout Git commit. Can you please add both of these e-mails into your Github profile (they can be hidden), so we can match your e-mails to your Github profile?

[nevins-b]

@karmi Added.

[ph]

I've merged your commit into #102, there is 7 integrations test that are currently failling taking a look.