LPS-17407 Style the Classic theme navigation for appropriate sub-menu appearance

http://issues.liferay.com/browse/LPS-17407

Jon,

Changes of note:
- node-menunav-core.css did not seam necessary as the classes needed were already being pulled in with: /html/js/aui/node-menunav/assets/skins/sam/node-menunav.css
- I moved all the macros from intit.* to init_custom.* as this seemed more appropriate to target just the Classic theme.
- _unstyled navigation.* has been left as-is.
- app_view_entry.css needed modifications to prevent IE6 from miss-applying chained (.class.class.class) selectors.

Byran