added responsive.layout.css import
Added responsive css file, icon images and edited css by adding new breakpoint rules Issue.#2671
Responsive implementation on basetheme, nav, widgets and responsive css files edited  for:
- Site name
- HWPI Bar
- Responsive menu & search css
- Main layout
- 2 col. layout
- 1 col. layout
- Sidebar collapse
- Calendar controls
.#2671
Created responsive files based on current base, layout, nav, widget and slideshow to aid in control for development
#2671
Created responsive files for the 3 themes and worked on responsive menus
Edited responsive CSS for Vibrant: menu, single and double column layouts and colors
os_slideshow: updatte weight
Edited CSS files for responsive 3 columns for all themes. Edited calendar controls.#2671
Slideshows: Implemented responsive CSS  for slideshow styles .#2671
Footer: Implemented responsive CSS on the three themes.#2671
#2755 #2671: Add js for menu toggling behavior in mobile menu.
Dropdown menu: Implemented show/hide CSS for all three themes.#2671
Merge pull request #2790 from openscholar/2671-responsive-css

2671 responsive css