Add a configuration option to keep terminals opened by apport opened

[Karl-Philipp Richter]

`gnome-terminals` which are opened by `apport` to monitor the installation of necessary deb packages for local investigation, production of `gdb` backtraces, etc. are closed immediately after success, but after failure as well (e.g. if `apt-get` can't get its global lock, or another issue occurs). For debugging `apport` it'd be very useful to have a configuration option which allows the terminals opened by `apport` to stay opened after a failure.

Some details and workarounds have been discussed at (this askubuntu.com question)[http://askubuntu.com/questions/600875/how-to-keep-terminal-for-installation-of-debugging-symbols-of-apports-local-inv].

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: apport 2.17-0ubuntu1
Uname: Linux 4.0.0-040000rc7-generic x86_64
NonfreeKernelModules: nvidia
ApportLog:

ApportVersion: 2.17-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Apr 9 15:24:55 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-04-02 (6 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Beta amd64 (20150326)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: apport
UpgradeStatus: No upgrade log present (probably fresh install)

[Karl-Philipp Richter (krichter722)]

A hint for the implementation has been given at http://askubuntu.com/a/609415/173287.

[Marcus Tomlinson (marcustomlinson)]

This release of Ubuntu is no longer receiving maintenance updates. If this is still an issue on a maintained version of Ubuntu please let us know.

[Launchpad Janitor (janitor)]

[Expired for apport (Ubuntu) because there has been no activity for 60 days.]