Manifest merger failed - allowBackup tag duplicated

[lwasylkowski]

Seems like the library project's manifest includes allowBackup and supportsRtl application attributes. I don't think these are necessary, since it's application's role to define whether it supports RTL/backup.

Right now the presence of these attributes is problematic, since if the consumer of the library explicitly sets allowBackup=false in their app's Manifest, the manifest merger complains about duplicate element, forcing the developer to use <tools:replace="android:allowBackup">

I'm happy to submit a pull request if what I say makes sense to you

[hbmartin]

Agreed - the tag is auto-generated when creating new libraries in Android Studio, but I can't think of any reason why it needs to be here.
#61