New filters for sidebar/content opening classes

New filters for opening main container classes:
- wflux_sidebar_1_with_content_1
- wflux_sidebar_1_no_content_1
- wflux_content_1_with_sidebar_1
- wflux_content_1_no_sidebar_1

This allow the addition of Flux Layout CSS classes to the core wrappers (especially useful for adding conditional media query classes for main content and sidebar!)