SerialTerminal: Select text in input line after each command

Makes it easier to type a different command.

Change-Id: Ica152575f2f5130a8f2da75379403841aba89176
Reviewed-by: Benjamin Balga <balga.benjamin@gmail.com>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/serialterminal/serialoutputpane.cpp

@@ -736,6 +736,7 @@ void SerialOutputPane::sendInput()
 
         current->writeData(m_inputLine->text().toUtf8() + m_serialControlTabs.at(index).lineEnd);
     }
+    m_inputLine->selectAll();
     // TODO: add a blink or something to visually see if the data was sent or not
 }