Second patch to address #2607

The wizard needs to be restored and rewound to the first page

First patch to address #2607

This should mostly fix #2105 and #2044

a3e7f513 broke them.

This fixes #2373

* Also ensure the maximum is always >= the current value.
* Take care to handle the ULLONG_MAX value that's sometimes used
  as _completedFileCount.

It also registers and unregisters the shell extensions properly and
forces explorer to reload/unload the DLLs so they can be removed.
This obsoletes #2377.

Fixes #2487
Fixes #2377

Issue #2591

This fixes mirall#2358

This fixes mirall#1132

A variable that counts the affected items of the propagator operation
done on a item was added to SyncFileItem. Usually that is 1 because
most operations affect only the item itself. But for removes, the
number can be higher for directories (one remove removes a whole tree).

Some rearrangements were needed.

* Also use readonly DB access for SocketAPI.

Issue #1989