[KitKat] Correct HCE permission, action, metadata

Switching the Permission, IntentFilter, and MetaData attributes to use
the built-in string constants prevents a few typos that were causing
trouble. After these corrections, the "Xamarin" service_banner.png
drawable will appear correctly under the top-level "Tap & pay" entry in
the Android Settings menu when the app is installed.

The correct Permission is:
Android.Manifest.Permission.BindNfcService ==
"android.permission.BIND_NFC_SERVICE"

The correct action in the IntentFilter is:
HostApduService.ServiceInterface ==
"android.nfc.cardemulation.action.HOST_APDU_SERVICE"

The correct MetaData name is:
HostApduService.ServiceMetaData ==
"android.nfc.cardemulation.host_apdu_service"


If the Permission is incorrect, the system will output an error to the
logcat log during app installation:

> E/RegisteredServicesCache: Skipping APDU service
> ComponentInfo{KitKat.KitKat/kitkat.HceService}: it does not require
> the permission android.permission.BIND_NFC_SERVICE


If the MetaData name is incorrect, the system will output a warning to
the logcat log during app installation:

> W/RegisteredServicesCache: Unable to load component info
> ResolveInfo{654f9948 KitKat.KitKat/kitkat.HceService m=0x108000}

> W/RegisteredServicesCache: org.xmlpull.v1.XmlPullParserException: No
> android.nfc.cardemulation.host_apdu_service meta-data


If all three attributes are correct, the system will automatically start
the service once it's installed:

> I/ActivityManager: Start proc KitKat.KitKat for service
> KitKat.KitKat/kitkat.HceService