rsbackup log format change

[Richard Kettlewell]

I just pushed the change referred to below.  This changes the rsbackup 
log format (to use SQLite).  Existing installs are upgraded to the new 
format automatically.

I've been running this code for a few days now without trouble, hence 
its public exposure.  If anyone feels like testing it I would be 
interested in any feedback.

Otherwise, just be aware that this change is coming in a future release. 
  There is no provision for downgrade; if you turn out to need it my 
advice will be 'restore from backup'!

> commit c842f3e9bb05067968cc68c1fdaabc939bc2053a
> Merge: 33a8f00 cbc23bf
> Author: Richard Kettlewell <rjk at greenend.org.uk>
> Date:   Wed Dec 31 17:29:27 2014 +0000
>
>     Merge branch 'issue11'
>
>     Logfiles are replaced by a SQLite database.
>     Old installations are automatically upgraded.
>
>     fixes #11

ttfn/rjk