Basic keyboard accessibility CSS tweaks

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).
Removed touchstart from bootstrap-dropdown.js.
Cleaned up dirty CSS

Used recess rather than less
Keyboard accessibility in documentation

Removed unnecessary (?) and harmful (from a keyboard access point of
view) tabindex=-1 in the documentation examples.
Splits the progress @echo statements in the Makefile.
Replaces some @echo recipes by @printf.

The echo command does not understand the -n argument on Mac OS X.
This is due to the fact that:

  - Makefile calls /bin/sh to execute a command
  - in Mac OS X, /bin/sh is a link to bash
  - in Mac OS X, bash is compiled with --enable-strict-posix-default

Therefore, the echo command does not have the -n argument.

printf on the other hand is a builtin function that works well on Mac OS X and Linux.
Moves one @printf statement to be more accurate.
Modifies the Makefile to use local npm install **when available**

The change introduced in 5bd8cdca9 was:

  - partial, as not all the command were translated
  - preventing the use of a global npm installation
Allows the user to set different source and destination in Makefile.

A user can use the following command to determine where to copy the resulting css file:

    $ BOOTSTRAP=<my-path> make
Changes some more commands to use the local npm install.
Revert "Keyboard accessibility in documentation"

This reverts commit a809daf2841f65ffac5030b2c6ce6aea60dd6233.
Leave tabindex=-1 alone

It seems that, as misguided as I personally think it is, ARIA does
indeed want dropdown menus not to behave as regular keyboard users
expect them, killing TAB/SHIFT+TAB in favor of cursor keys. Fair
enough, the issue I have is then with ARIA, not with bootstrap. I would
sugges thought that if you really do want to follow ARIA consistently,
*any* navigation bar should also become an ARIA menu, further making it
impossible for keyboard users to use TAB/SHIFT+TAB to navigate through
it, and that these changes should be reflected in the bootstrap
examples as well...
Revert "Leave tabindex=-1 alone"

This reverts commit 370fa45fbe4ee879a626a67bb4df0ec9495102be.
Fix that thing with disabled buttons changing color on hover
Forgot to add built docs css file
Fix logic error where a disabled button would change color in an enabled fieldset
Update Recess version
IE8 compatible fix for disabled button hover
Update less/mixins.less

horizontal three color gradient added
Tooltip positionning on special cases