Restricted account visibility

When accounts are shared to a restricted/limited user, apps can
opt-in to viewing accounts of a certain type. Other shared accounts
are not visible to the app.

App would specify the account type in the manifest <application> tag
with the attribute restrictedAccountType="foo.bar", where "foo.bar"
is the account type as defined by the authenticator.

Change-Id: I7586da04d6d6d32aae15adc6b1366f325bb07384