Backup exclusion of shared prefs on android in the library itself

[Redth]

We show in the sample how to exclude Android's shared preferences for the essentials file from backup but let's see if we can find a way to make this included as part of the library.

We might be able to have the application manifest declaration merged and include the XML as a resource file.

Worth exploring this issue.

[jamesmontemagno]

Todo:

• Add a default xml file with 1.0
• Update docs to require this setup and document how to use our file or point to custom file implementation

[jamesmontemagno]

After investigating the xml is bundled up into the library and then into the app, however ${applicationdId} doesn't get update in library resources only attributes in the code :( so for this reason we can't add this in. However we will update the docs.