Add documentation.

Contributes to CURA-5786.

resources/qml/ActionPanel/ActionPanelWidget.qml

@@ -8,6 +8,10 @@ import QtQuick.Layouts 1.3
 import UM 1.2 as UM
 import Cura 1.0 as Cura
 
+
+// This element hold all the elements needed for the user to trigger the slicing process, and later
+// to get information about the printing times, material consumption and the output process (such as
+// saving to a file, printing over network, ...
 Rectangle
 {
     id: actionPanelWidget

resources/qml/ActionPanel/OutputProcessWidget.qml

@@ -8,6 +8,11 @@ import QtQuick.Layouts 1.3
 import UM 1.1 as UM
 import Cura 1.0 as Cura
 
+
+// This element contains all the elements the user needs to visualize the data
+// that is gather after the slicing process, such as printint time, material usage, ...
+// There are also two buttons: one to previsualize the output layers, and the other to
+// select what to do with it (such as print over network, save to file, ...)
 Column
 {
     id: widget

resources/qml/ActionPanel/SliceProcessWidget.qml

@@ -9,6 +9,10 @@ import QtQuick.Controls 1.4 as Controls1
 import UM 1.1 as UM
 import Cura 1.0 as Cura
 
+
+// This element contains all the elements the user needs to create a printjob from the
+// model(s) that is(are) on the buildplate. Mainly the button to start/stop the slicing
+// process and a progress bar to see the progress of the process.
 Column
 {
     id: widget