New stuff:
* Adds `.has-feedback` and `.form-control-feedback` to show icon-based
form feedback to users. Fixes#11836.
* Removes the `width: 1em` on `.glyphicon` because it makes it
impractical to resize the width of all icons, even if they’re not
“empty” (e.g., a simple `.glyphicon { width: 30px; }` wouldn’t work,
nor would a class preceeded by a parent class.
Clean up:
* Sets `width: auto;` on all `.form-control`s within inline forms.
* Removes all the inline `select` menu `width` styles because all
inputs are now `auto`.
* Update form states docs to separate out sections better.
- Also fixes the vertical alignment of labels in horizontal layouts on
account of the recent button and input padding changes
- Also changes the vertical alignment of the checkboxes and radios in
horizontal forms
* Moves input groups CSS into separate file
* Moves input groups docs into the Components page
* Add support for radios and checkboxes in input groups to fix#8679
