Remove AdSupport.framework

Facebook have officially removed `AdSupport.framework` from their podspec: [facebook/facebook-ios-sdk/pull/658](https://github.com/facebook/facebook-ios-sdk/pull/658/files)

Also see the following comment from @chrisp-fb:
> Thanks for all the comments. We'll update our 3.19 cocoapods spec soon ([#658](https://github.com/facebook/facebook-ios-sdk/pull/658)) to not include the AdSupport.framework by default. If you are still seeing problems and verified no other libraries are accessing the advertisingIdentifier, please submit a report to https://developers.facebook.com/bugs with relevant information such as how the SDK is integrated (download, cocoapods, or something else) and what other third party libraries you're using. Thanks.

I have no problem running the current version of phonegap-facebook-plugin after removing `AdSupport.framework`.

Hopefully this would also solve the problems in #719 and #661 

@aogilvie what do you think?

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I also did a little clean-up of the `plugin.xml`:
- [x] Standardize indentation/whitespace
- [x] Update the plugin namespace to Apache Cordova NS instead of Phonegap NS
- [x] Remove unnecessary `window` in `<js-module>` `<clobbers>` target:

> `<clobbers target="some.value"/>` indicates that the module.exports is inserted into the window object as window.some.value.