Server discovery

Hi Dave,

I'm a bit unhappy about the current server discovery feature.
First of all, on machines without pgsql wx will barf about a missing
registry key with a message box, quite ugly.

Second, the generated server info can't be edited. Well, currently this
isn't possible for manual entered servers either without registry
editing, but we should change that anyway: there's no reason why we
don't have a dlgServer.cpp except for "it's not done".

My thought was to push the service information into pgadmin registry
values when installing, so the settings can be adjusted later.

Regards,
Andreas