Feature suggestion: Indexing state indicator

[froghunter]

It would be nifty to have some way of seeing a couple of things about indexing:

Is indexing complete? If not:

1. Allow the user to toggle on a notification in the Android notification bar.
2. Make available the current percentage of content which is indexed.
3. If reasonably possible to implement (not a given, by any means...), an estimated time to completion.
4. An explicit "start indexing now" button.