Allow the plugin to be installed into the python site-packages directory

[Peter Kropf]

Here's a snippet from a trac mailing list thread that hints at the problem:

Hmm.  I tried, actually, putting the [graphviz] section in the main trac.ini,
but it didn't work.  Maybe if I'd put the egg in the main plugins section
(trac/plugins) *and* put the [graphviz] section in the main conf/trac.ini it'd
work.  (And then enable it there too).

Let's see... (goes away to try it)... nope.  I get a red box with  Error:
Failed to load processor graphviz / No macro named [[graphviz]] found.

Actually, never mind -- I see that trac doesn't actually load plug-ins from
trac/plugins.  I don't even know how that dir got in there.  It wants them to
be in the python site-packages dir.  But when I put them there, I get a
message from the egg that there's no [graphviz] section in my .ini file.  It
seems like it really wants that to be in the site/conf/trac.ini.

Anyway, I just put it all back into the site dir and it works fine.

[Peter Kropf]

Fixed with release v0.6.2.