DBusTest: Add test for Window interface methods
Tested functions:
- int sessionCount();
- QStringList sessionList();
- int currentSession();
- void setCurrentSession(int sessionId);
- int newSession();
- int newSession(const QString &profile);
- int newSession(const QString &profile, const QString &directory);
- QString defaultProfile();
- QStringList profileList();
- void nextSession();
- void prevSession();
- void moveSessionLeft();
- void moveSessionRight();
- void setTabWidthToText(bool);