Use fallback MMS attachment name if can’t create file with received name

Received MMS location may be encoded using RFC 2047 (e.g. for messages
sent from old Nokia phones) or may contain characters illegal in file names.
RFC 2047 decoding is currently not implemented so fallback name
should be used in such case. I also changed fallback name to be
a human readable localized text instead of hex message id.

Change-Id: Id19fa127c0cfc68679232225bfb17b3c6514524b
Mms: sets endMmsConnectivity() as last operation

When a user receives an Mms and there is no more pending requests, the method
endMmsConnectivity() is called to turn the data connection off and clear the
wakelock. Sometimes the phone deep sleeps before the user gets Mms
notifications, so this patch makes endMmsConnectivity() to be the last
operation so users can be notified of Mms's.

Patchset 2: changed boolean mEndMmsConnectivity to needToEndMmsConnectivity

Change-Id: Iff518acbf98486ede7f24e1439b021d26cdbccc1