[mythtv] Mythvideo and fanart - minor defects

[paul10 at planar.id.au]

Love the look of this new patch.

I recompiled and used this today - and I think found two problems:
1.  I set the directory I wanted it to store the fanart in through
settings, but it seems to be still trying to store to the default.  The
cause seems to be that the setting is written into "mythvideo.fanartDir"
in teh settings table, but the code is looking for "VideoFanartDir". 
There are a bunch of settings that are prefixed with "mythvideo.", so I'm
assuming this is the preference, I'll submit a defect with a patch
attached.

2.  It only attempts to download fanart or posters if there isn't already
a poster there.  Ideally resetting metadata would cause it to re-download
all posters, but certainly if I'm going to grab fanart for the things that
are already downloaded, I'd rather not have to go and delete all my
existing posters first (only some of them came from online, so will be
quite tedious to go through one by one deleting only those that I want to
download fanart for).  This one looks to be a conscious choice, but
perhaps one we should think about.  I won't submit a patch without some
discussion.

Thanks,

Paul