fix in DateTimeTrigger management and executions when service already stopped

app/src/main/res/layout/activity_manage_specific_poi.xml

@@ -57,7 +57,7 @@
                 		android:layout_width="wrap_content"
 			            android:layout_height="wrap_content"
 			            android:ems="10"
-			            android:inputType="numberSigned" />
+			            android:inputType="text" />
 			        
 			    </TableRow>
 			
@@ -78,7 +78,7 @@
 						android:layout_width="wrap_content"
 						android:layout_height="wrap_content"
 						android:ems="10"
-						android:inputType="numberSigned" />
+						android:inputType="text" />
 				</TableRow>
 			    
 				<TableRow