AutomatableModel: made member variables private again

As of commit dd28a654b5 some member
variables were made protected without any actual requirement for it.
Revert the part of the commit.

src/core/AutomatableModel.cpp

@@ -44,11 +44,11 @@ AutomatableModel::AutomatableModel( DataType _type,
 						const QString & _display_name,
 						bool _default_constructed ) :
 	Model( _parent, _display_name, _default_constructed ),
-	m_minValue( _min ),
-	m_maxValue( _max ),
 	m_dataType( _type ),
 	m_value( _val ),
 	m_initValue( _val ),
+	m_minValue( _min ),
+	m_maxValue( _max ),
 	m_step( _step ),
 	m_range( _max - _min ),
 	m_journalEntryReady( false ),