auth-dialog: add desktop file for auth dialog

NM-openswan was missing support for nm-openswan-auth-dialog.desktop.in.in.
So added a new nm-openswan-auth-dialog.desktop.in.in, and modified
related Makefile and configure.ac files.
build: require Networkmanager 0.9.8 or later
trivial: remove dead code based on coverity scan

And move setup_password_widget() higher to fix missing prototype.
properties: fix prcoessing of nm-openswan-dialog.ui file
openswan/libreswan does not provide tun0 interface, so fixed the code where it sends tun0 interface.
Fixed an issue where writing configuration on stdin should not end with \n as it gives error. It used to work previously, but not with latest versions.
Fixed more coverity scan issues.
trivial: remove some dead code
core: fix handling of pluto child processes

Rewrite pluto watch API which watches the pluto process for its status.
Fixed memory leak issues as not all child processes were reaped correctly.
Also g_spwan_close_pid was not being called after children were reaped.
Also modified debugs and added more to help with debugging in the future.
Fixed defaults values for more parameters to help the VPN connection stay more reliable.
properties: fix instantiation from control-center (bgo #720319) (rh #1040924)

->get_widget() was returning a widget that already had a parent
instead of a stand-alone widget which we could pack as we pleased.

This fixes the IPSec VPN dialogue in gnome-control-center's Network
panel not working.

See https://bugzilla.redhat.com/show_bug.cgi?id=1040924

https://bugzilla.gnome.org/show_bug.cgi?id=720319