change sidebar display order

I'm proposing here that the left and right sidebars swap firing order in `widgets_init` for a more user friendly approach. From what I can tell, the right sidebar is the only one used by default in the customizer options (checked). So without actually going into the customizer to set things up, it'll be ready to display on everything but posts and pages. 

As we all know, the widgets.php UI expands the top sidebar area by default and collapses all others. With no clear indication of how the sidebar system works at this point (remember, they haven't been in the customizer yet **and** it's always possible that using a widget in a sidebar area is what makes it appear), loading the first sidebar area with widgets, which is the left sidebar as of now, can be a few wasted minutes and a lot of confusion for average users.

I call to display the right sidebar first and have that area expanded by default just for a smarter UI.