Topic/cli install

The main idea of this pull request is to remove the need to embed any files from the iOS/Android SDKs and allow for the installation of the plugin to be done solely through the command line interface.

As a cautionary note, these changes are still in-progress, but I wanted to start this discussion to get feedback and see if any of these changes are of interest. In the current state, based on commits from @wedgybo and @Alexandre-Georges, the plugin is working on Phonegap 3.2 on both iOS and Android.

Since the result of this pull request would no longer include the SDK files, the SDKs do need to be installed locally, but one idea to help make these steps more straightforward could be to create optional hooks scripts to make the necessary updates.

Also, if phonegap/phonegap-cli#195 is incorporated, then the `plugin.xml` could be used to take care of the configuration pertaining to the Facebook app ID and display name, and the hook scripts could just be used to bring in the SDKs. I can elaborate more or provide examples of the hook scripts if need be, but note that no SDK files need to be copied into the project. For iOS, the FacebookSDK framework is referenced and for Android the Facebook SDK library is referenced as an external library in the `ant.properties`.

I think these changes may require a bit more testing, but I wanted to bring them up sooner rather than later to get ideas and gauge interest.

PS - I am not sure how compatible these changes are with the Phonegap automated build process, but perhaps this should be weighed into the discussion.