HY-1666 Add options to scrollbars

## Problem

Right now scrollbars can only be configured through CSS, some of the options should be able to be configured through code.

## Solution

Allow options to be configured through code.

## Tests

Added.

## QA / +10

Check out branch. Tests should pass, no regressions.
What happens if no thickness options are provided and these css styles are set to 'px?'   Browsers okay with that?