Reuses the "commiting" message to indicate how many apps have been
processed so far.
Refactors existing progress handling between `RepoUpdater` and
`UpdateService` to use `LocalBroadcastManager` in preference to
`ProgressListener`. Still needs to use `ProgressListener` to talk
between `RepoUpdater` and the `Downloader` +
`ProgressBufferedInputStream`.
The only change that is related to something more important than
notifications is the fact that now `IndexV1Updater` makes use of the
`indexUrl`. To do so, because it is final, the base class constructor
delegates to `getIndexUrl()` which is overriden by the v1 updater.
This is required because we want to differentiate between broadcasts
coming from different repo update processes.
Fixes#1054.
df20d2df8d