Allow to select interest groups for campaign in the campaign form

I 've successfully applied this patch and looks good to me. That's why RTBC'ed!

Setting back to needs review because it needs more testing.

When you add a campaign on Mailchimp's website it looks like this (attached). You have the option of sending it to a Group. You can choose "Contacts match any/all of the following conditions:" And the conditions include your groups on this audience (in the picture it's "Audience for Debugging" for which you can choose "one of / all of / none of" and then select multiple items from the list box.

Providing the much simpler form on the Drupal site is not adequate. In the example "Expert / Intermediate / Beginner" are presented as radio buttons, which means you can only select one. There's no option for "one of / all of / none of". It is difficult to un-select a radio button if a stray click selects one by accident. Better to not provide this feature. If we are going to provide it, it needs more work.

Basically a re-roll of #1 Also changed Array() to [] , fixed typos in a comments, changed tabulation from 4 to 2 spaces, removed some extraneous whitespace. Was secretly hoping this would still work so I could address the issues in #7 tomorrow.

Unfortunately, more needs to be changed apparently because this version is not storing any campaign. It just returns you to a blank 'create campaign' page after pressing save (without error / feedback unfortunately.)

BTW all the patches in this issue also incorporate the fix in #3079700: saved_segment_id attribute should be optional when a campaign has segment options

Overhaul of patch in #2 but taking into account the concern raised in #7. Hope this is ok for you now @rjacobsen0
I would love some feedback on this patch, please try it out.

For it too work properly, it needs patches from #3079700: saved_segment_id attribute should be optional when a campaign has segment options, #3156283: Can not save campaign without 'saved_segment_id' and #3008883: Selected list segment not showing on Mailchimp Campaign view page, causing errors hopefully these will get committed soon.

Added the "Segment Operator" to give users the choice of "interestcontains", "interestcontainsall" or "interestnotcontains"
And did a bit of clean up (removed debug code etc)

No interdiff as there is no review yet of previous patch anyway.

Thanks for your commits everyone!
Combining patches 11 and 12 and reviewing them.