Support pre-HC style account shortcuts

Account shortcuts used to point at MessageList directly with a
content://com.android.email.provider/account/ACCOUNT-UUID URI.

Hook these intents and open Welcome instead.

On Eclair and before, we stored an account-ID directly as an extra,
but this style is no longer supported.

Bug 4208879

Change-Id: I9fecb0723743377a6d7c7e84626e8613f2356492
6 files changed