gpgconf support added to GPA

Hi,

with the latest gpgme 1.1.6 and gpa trunk in SVN, a new menu entry appears:

Edit->Backend Preferences...

Selecting this entry pops up a dialog box where you can edit the
configuration of the crypto backends (gpg, gpgsm, dirmngr, gpg-agent etc)
using the gpgconf facilities (now provided by GPGME experimentally).

Because using gpgconf is a bit slowish, we only apply all changes as a
whole (thus not following the GNOME interface standard strictly).
There is an apply and reset button in addition to the usual cancel and OK.

You can find an example dialog at (not a permanent location)
ftp://ftp.g10code.com/g10code/scratch/gpgconf.png

Maybe check it out and let me know what you think.

Thanks,
Marcus