Call ProcessInfo::readArguments when ssh is detected

When ssh is run via 'exec ssh ...', ProcessInfo::_arguments is not updated since ProcessInfo::readArguments is only called once when the process is started. Thus, SSHProcessInfo::SSHProcessInfo will have soft errors since it relies heavily on reading ProcessInfo::_arguments which are unfortunately outdated. Implements UnixProcessInfo::readArguments which reads /proc/[pid]/cmdline and will be used by LinuxProcessInfo and SolarisProcessInfo to reduce code duplication. Also implements ProcessInfo::refreshArguments which calls ProcessInfo::clearArguments and ProcessInfo::readArguments in order. A solution is to call ProcessInfo::refreshArguments whenever ssh is detected in Session::getDynamicTitle.