Use FileProvider rather than sharing raw file URI

Adresses the following crash that happens after receiving
an object over Nfc:

 Caused by: android.os.FileUriExposedException: \
        file:///storage/emulated/0/beam/vcards_20160804_140145.vcf \
        exposed beyond app through Intent.getData()
    at android.os.StrictMode.onFileUriExposed(StrictMode.java:1799)
    at android.net.Uri.checkFileUriExposed(Uri.java:2346)
    at android.content.Intent.prepareToLeaveProcess(Intent.java:8967)
    at android.content.Intent.prepareToLeaveProcess(Intent.java:8928)
    at android.app.PendingIntent.getActivity(PendingIntent.java:340)
    at com.android.nfc.beam.BeamTransferManager.\
            updateNotification(BeamTransferManager.java:331)
    at com.android.nfc.beam.BeamTransferManager.\
            updateStateAndNotification(BeamTransferManager.java:365)
    at com.android.nfc.beam.BeamTransferManager.\
            processFiles(BeamTransferManager.java:429)

Test: Non-media file transfer using beam
Bug: 30883785
Change-Id: I28befb70743ae84825b4459d1433e8982b0a74ac