Documented the purpose of various perl modules.

lib/Slic3r/GUI/Plater/2D.pm

@@ -1,3 +1,6 @@
+# 2D preview on the platter.
+# 3D objects are visualized by their convex hulls.
+
 package Slic3r::GUI::Plater::2D;
 use strict;
 use warnings;

lib/Slic3r/GUI/Plater/2DToolpaths.pm

@@ -1,5 +1,6 @@
 # 2D preview of the tool paths of a single layer, using a thin line.
 # OpenGL is used to render the paths.
+# Vojtech also added a 2D simulation of under/over extrusion in a single layer.
 
 package Slic3r::GUI::Plater::2DToolpaths;
 use strict;

lib/Slic3r/GUI/Plater/ObjectCutDialog.pm

@@ -1,3 +1,6 @@
+# Cut an object at a Z position, keep either the top or the bottom of the object.
+# This dialog gets opened with the "Cut..." button above the platter.
+
 package Slic3r::GUI::Plater::ObjectCutDialog;
 use strict;
 use warnings;

lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm

@@ -1,3 +1,6 @@
+# Configuration of mesh modifiers and their parameters.
+# This panel is inserted into ObjectSettingsDialog.
+
 package Slic3r::GUI::Plater::ObjectPartsPanel;
 use strict;
 use warnings;

lib/Slic3r/GUI/Plater/ObjectSettingsDialog.pm

@@ -1,3 +1,7 @@
+# This dialog opens up when double clicked on an object line in the list at the right side of the platter.
+# One may load additional STLs and additional modifier STLs,
+# one may change the properties of the print per each modifier mesh or a Z-span.
+
 package Slic3r::GUI::Plater::ObjectSettingsDialog;
 use strict;
 use warnings;

lib/Slic3r/GUI/Plater/OverrideSettingsPanel.pm

@@ -1,3 +1,6 @@
+# Included in ObjectSettingsDialog -> ObjectPartsPanel.
+# Maintains, displays, adds and removes overrides of slicing parameters for an object and its modifier mesh.
+
 package Slic3r::GUI::Plater::OverrideSettingsPanel;
 use strict;
 use warnings;