Revamp terminalStrip feature code

Move RealTerminal class in a new file
Move PhysicalTerminal class in a new file.
Remove the use of QWeakPointer and use instead QSharedPointer
in a big part of the revamp.

sources/TerminalStrip/UndoCommand/changeterminallevel.cpp

@@ -16,6 +16,7 @@
 		along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include "changeterminallevel.h"
+#include "../realterminal.h"
 
 ChangeTerminalLevel::ChangeTerminalLevel(TerminalStrip *strip,
 										 const QWeakPointer<RealTerminal> &real_terminal,