macosx: Remove subviews from home view stack view when deallocating the home view stack view controller

Turns out when switching views and deallocating the home view stack view
controller we were not emptying out the subviews for the actual stack
view, which had a reference held on it by the library window.

This means the created containers would stay alive and included in the
home view stack view's subviews... Then when switching back to the home
view we'd initialise a new home view stack view controller, which would
initialise new containers, and then add them to the home view stack
view, creating duplicates

Signed-off-by: Claudio Cambra <developer@claudiocambra.com>