NFC: Move NFC service implementation out of system_server.

NFC service is now an application service in packages/apps/Nfc.

NFC service is registered through ServiceManager.addService(), and the proxy
object NfcAdapter obtains a handle to it through ServiceManager.getService().

**Important** Had to add new symbols AID_NFC / NFC_UID / android.uid.nfc and
modify service_manager.c, Process.java and PackageManagerService.java in order
to force the com.android.nfc process to take a fixed uid, so that it can use
ServiceManager.addService().

Most of the JNI has moved to packages/apps/Nfc/jni. However NdefRecord and
NdefMessage require some in-process native code, so android_com_NdefMessage.cpp
and android_com_NdefRecord.cpp stay in frameworks/base/core/jni. They link to
a very small library libnfc_ndef.so that implements NDEF message parsing. This
has been added to core.mk so all devices (even without NFC hardware) can work
with NDEF data.

Bug: 3041259
Bug: 3097445
Change-Id: If7f00cd8f2053acfc9319ca366d4a9c02bd396e6
Signed-off-by: Nick Pelly <npelly@google.com>