Added GLFW_DONT_CARE.

This changes the behavior of framebuffer hints set to zero.  Before,
zero meant that any value was acceptable.  This changes zero to be an
explicit preference and adds GLFW_DONT_CARE to mean that any value is
equally acceptable.

Fixes #70.
Added GLFW_DOUBLEBUFFER.
Added glfwGetKeyName.
Added glfwSetSizeLimits.
Added position testing to windows test.
Added GLFW_FLOATING.

Fixes #23.
Updated glad.
Fixed plural forms on key/button arrays.
Made windows test show all windows at once.
Setting CSS for missed elements.
Doxygen CSS cleanup.
Introducing extra.less and using Less CSS for higher flexibility.

This will reduce the amount of copy paste involved when performing
slight changes to the default color sets.

These Ruby gems are required for generating extra.css from extra.less:
gem install less therubyracer

Please run this command to regenerate extra.css:
lessc --compress extra.less > extra.css
Formatting.
Documentation work.