Added a WANT_CONTACTS intent extra to indicate that we want to export...

...contacts to storage. This intent extra is then used in the Contacts app to
 ignore the MAX_CONTACTS_NUM_TO_SELECT_ONCE value so that we can export
 any given number of contacts to storage.

Change-Id: Id3f39b30c545acde1014a4d2a860d5ef022a1b28