This reverts merge request !108

Set default account status to available

Add 'debug' / 'verbose' options for libpurple debug output

- the attempt to launch another Chatty instance led to a core dump crash
- Chatty won't also start now, if another libpurple client, like Pidgin, 
is running already

add support for load/unload plugins

Add gtk application name

Apply some changes to auth-request dialogs
Improve SMS plugin handling

Add a dialog for accepting/rejecting XMPP authentification-requests

reintroduced 'lurch' since it is more actively maintained and more 
widely used than the 'libpurple-omemo-plugin'

Entirely implemented in the applications code

The printf would need to use stderr anyway so lets use glib's function
right away.

This disables them by default and allows them to be enabled via
G_MESSAGES_DEBUG=all or G_MESSAGES_DEBUG=<logdomain>

Add preferences support; load the OMEMO plugin automatically if present in the ./purple/plugins folder