Fix some possible "Precondition Failed" bug

The problem was if there was a false conflict: the file has been touched
both on the server and the client.
 - etag has changed on the server
 - mtime has changed on the server and the client and is the same
 - and file size is the same on both the server and the client

This may also happen if the file is uploaded on the server, but the client
looses connection (or crashes) before it get notified of the etag.

In both tree, the instruction is EVAL, but we reduce it to a NONE because
we detected that the conflict is 'false'.  Still, we need to update the db
with the new etag.  (_should_update_db)
The problem was that we would set the flag on the wrong tree.
This was not a problem when the file was NEW on both side since  we checked
for null etag and used the other one then.
Fix syncing a folder with '#' in the name

Or an url with '#'

Fixes #1838

The problem is a bug fixed in Qt5 now breaks.
In Qt4, QUrl::setPath() did not properly handle path with '#' in them
and QUrl::toString would restitute the '#'.

But csync will blindly do  "uri + path" before passing the path to
VIO.  because csync_update has no idea that the VIO plugin need special
encoding, the encoding cannot be done there.  But csync_owncloud then
encodes the full path.  So if the uri contains '#', it must not be already
encoded or there will be two encoding.
Propagator: Recover from 'precondition failed' error

When we detect a precondition failed, it is possible that it is
because the etag in the database is wrong.  We must therefore not
read from the database on the next sync.  In order to avoid that, we
reset the etag of parent directories to invalid values

Fixes #1767
Optimize move

Do not send the mtime for each file without a directory, because the server now keeps it
test fles with '%' and '#'
Merge branch '1.6'