* Added a new mixin to calculate rems and pixels for IE fallback
* Updated the body, p, and .lead elements to use the new .font-size() mixin
* New mixin has default value of 14px or 1.4rem
* Still needs exploration, and change this means lots of work rejiggering margins and line-heights
* Related, started to reorganize the mixins a bit to call out mixins that are used by the framework and not utilities or snippets

* Same code, but different classes was confusing
* Now .img-thumbnail just extends .thumbnail

Mostly doubling-up :hover styles to also cover :focus, as a first step
to making the framework more keyboard-friendly.
Additionally, fixed two small markup issues in the docs/examples to
make the "Learn more" large primary button-styled links
keyboard-focusable (as without href they're treated as non-tabable
anchors).

* Port print styles from reset.less to scaffolding.less
* Port responsive image styles from reset.less to scaffolding.less

remove .border-radius mixin and replace with standard border-radius property, since -webkit-* and -moz-* are only needed for older versions

fix static navbar container issues, clean up docs presentation by unfixing the top navbar in favor of static one, start adding table of contents for longer sections of docs

fixes #3210: add .btn to .navbar-form to remove bottom margin, improve vertical align of contents of .navbar-form

Rather than having a partial reset with individual elements having
their styles built back up, only elements without replacement
styles have specific properties 'reset'.

This commit also includes: a correction to the font mixin arguments
used on forms (the output is now valid CSS); the removal of
`overflow-y:scroll` from the `html` element which is now known to
cause some problems for jQuery modal plugins in Firefox.

breaking out patterns.less even more, removing unnecessary div from checkbox and radio lists--now just labels and inputs