Update "CHANGES.rst" file.
Update "sIBL_GUI_Manual.rst" file.
Fix invalid help file link.
Raise package release version number to "4.0.6".
Replace "Py2App" by "Pyinstaller" on Darwin Os.

Closes #175.
Update "darwinBuild.sh" build file.
Handle Python 2.6.x related exception in "inspector" component.

Closes #176.
Handle exception in "loaderScriptOptions" component when an attribute has undefined type.

Closes #177.
Attempt to fix "RuntimeError" exception in "preview" component.

Closes #178.
Handle "AttributeError" exception in "inspector" component.

Closes #179.
Code formatting.
Remove unused import.
Handle "shutil.copytree" related exception in "database" component.

Closes #180.
Handle exception in "databaseOperations" component while updating an ibl set file location.

Closes #181.
Handle exception in "sIBLeditUtilities" component when attempting to edit an ibl set and nothing is selected.

Closes #182.
Handle exceptions raised by actions triggered when "inspector" component has no active ibl set.

Closes #183.
Update "silb_gui.components.database.operations.updateItemContent" definition.
Fix duplicated languages in "scriptEditor" component on Windows Os.

Closes #170.
Update "sIBL_GUI_Manual.rst" file.
Update "Development" layout restore handling.