Import base css and pix into Bootstrap

So, it's been a while since I worked on a Bootstrap theme that inherited from Base. I've now been having flashbacks to how pointlessly frustrating that was.

This was the eventual solution I found. Import all the base css and pix directly into the Bootstrap theme as it then allowed more fine grained control over inheritence, in particular I could

a) delete CSS rule that were no longer necessary, which tidies things up and saves download time,
b) delete stuff that was actively messing up Bootstrap, which is very satisfying after you've spent weeks painstakingly working around it purely via CSS,

and since I was also using LESS I could:

c) use LESS to put fonts and colors into variables, and generally organise things better

I already found one bug in admin.css just by changing the filename to .less and running it through the compiler.

This makes even more sense now, since we're effectively writing the replacement for Base and the CSS contained within these core files is overdue for a spring clean.