Bug 969136: Update NFC Manager to handle Tag Discovered, empty tags, and unformatted tags.

This patch does a few things. Totally factory fresh NFC tags (used tags are not always resettable to factory clean state) are supported with this patch.

- NDEF also handles the case of no records being returned (as they are not formatted)
- NDEF_WRITABLE is added to NFC Manager to handle the case where NDEF is not specified as a tech type.
- The application, will now get a nfc-tag-discovered if it hits the default case.