Add support for static RadioCapabilities.

Some RILs don't support RIL_REQUEST_GET_RADIO_CAPABILITY.  Add
code to RIL.java to notice a REQUEST_NOT_SUPPORTED response and
check config.xml (config_radio_access_family) for a static answer.

Also catching GENERIC_FAILURE responses because Hammerhead modem
returns that.  B 21079604 created for this.

If neither Modem nor config.xml provide data, uses RAF_UNKNOWN
so we don't lie about capabilities and also so we fail fast
(setPreferredNetwork won't work).

bug:20561357
Change-Id: I9607e8e99242c6f7a6e330741d4afe8bbd08b1e7