- header was not collapsing properly when logo, site name and site slogan are disabled

Fix issue #856328: "Large empty space between primary links bar and content when site logo and site name disabled"

- layout width, min-width and max-width are now configurable
- position of each sidebar is configurable
- reduced header size
- removed $header and $footer regions
- added support for drop-down menus
- increased default height of textareas

Fix issue #829244: Remove strong borders from tables on admin/structure/block and admin/people/permissions