Manageable list of definitions

[Seva1986]

Take the opportunity to control the width of the indentation at .dl-horizontal using col-* by analogy like .form-horizontal.
And no need to make bold and align with the right dt, if necessary you can do yourself with the help of the classes and tags such as < b > and .text-right.

[mdo]

First part is a dupe of #11639. Second part we'll be leaving as-is.