Updates SASS variable names / CSS updates

- Updates SASS font family names, to fit generic->specific naming
convention.
- Updates text color to use function instead of _darkest variable.
- Removes underlines from header link buttons.
Floating header and search style updates

- Broad updates to floating header, such as including map zoom control
and search summary in static header state.
- Updates main search form inputs to simplify appearance.
- Updates mobile styles to exclude page numbers from pagination UI
control.
Removes big button styles

The big button style wasn’t used anywhere, so this removes it.
Adds pagination partial and results list footer

Adds pagination partial and includes partial in new results list footer.
Updates header summary
Removes letter spacing in small button
General style updates / Updates no results styles

Updates no results page styles and performs general style updates to
use variables for font sizes.
Formats variable names for consistency

Underscores variable names instead of dashes.
CSS cleanup

General formatting updates across base CSS.
Removes excess SASS color variables

Addresses part of #359. The greyscale variables numbers should still be
reduced as well.
Removes rhythm variables and goes with the defaults
Updates broken variable reference
Removes unneeded link_header variables

link_header and link_header_hover variables would be better to
encapsulate in a component, so this removes the variables.