Site Links code needs to be changed to use feed services

The Google API upgrade will eventually use feed services for site links, so the Optus project needs to change its implementation to use this service.

As much as possible, the implementation should be consistent with AML's FeedService implementation for call extensions. As of 2013-07-16 there are a few big differences that will need to be addressed in this feature:

-AML DAOs are not complete; currently feeds can only be added but the logic for updating and removing a feed is missing
-sitelinks should implement both but implementing "updating" as a remove then add is acceptable since that's how legacy sitelinks work. Of course it'd be better to make use of Google's update functionality so the sitelink doesn't lose performance data
-AML's implementation assumes 1 FeedItem per campaign
-, and assumes each campaign within an account has the same FeedItem-
-note that as of July 17th EST AML decided to give each CampaignFeed its own FeedItem
-for sitelinks, there can be many FeedItems per campaign, and we cannot assume FeedItems are identical across the campaigns (because the destinationURLs can differ)

As a baseline for this feature I have imported the GCE classes / Feed tables into 1.5.4 in the following git commits:

https://github.com/thesearchagency/core/commit/772e6e35a24782144595bba4bd8b12e1e256d206
https://github.com/thesearchagency/core/commit/9248e19a5f4fb951dd6e643b526bc0b57fe71965

I have also done a diff between AML's master and the branch these changes are being made on. I have brought in most of the necessary new files and edited a few existing files (see 1st commit above). It will be useful to look at git core google-extension branch to see the changes that have been made, as Optus is to use this as a template for updating sitelinks to use the FeedService. The diff results are attached and relevant as of 2013-07-16 US/Eastern.

QA please review all the notes in here and the subtasks for creating test cases. Also review Google's documentation (ie. https://developers.google.com/adwords/api/docs/guides/feed-services) which will help you better understand the workflow.

Release notes are in core/releases/1.5.4. I recommend QA takes note of all the new tables b/c you'll need to be familiar with them and how they relate to Google's Feed Services.