refactored css for sections and added enrollments

made the css that I used to create the sections a little more generic,
and moved the css out of the sections stylesheet into the
framework_and_overrides stylesheet.  Now these classes can be used
anywhere to create panel sections:

.panel-body-section: the base class for defining a section within a
.panel-body
.panel-body-section-heading: wrap a section heading in this class
.panel-body-section-title: inside a .panel-body-section-heading, use
this class to define the title element (e.g., <h4
class=“panel-body-section-title”>.panel-body-section-title</h4>)
.panel-body-section-row: a row within a .panel-body-section

See the ‘sections/_section’ or ‘enrollments/_enrollment’ partials for
examples.