SASS compilation variable conventions update, focusing on basic colors, baseline variable usage for padding and margins, ui-depth extends, along with other small fixes. The intent with this is to not have any user-facing impact, and instead move us closer toward having files that use our newer sass conventions.

* moving font-size to use @include font-size() mixin
* re-organizing vendor reset styling into _vendor.scss override rather than _reset.scss
* initial rule re-organization and minor line-height tweaks

Bourbon's box-shadow mixin has been deprecated, and they recommend to use the
official spec.

typography, SASS import, mixins/extends

studio - resolved z-index issue with release date modal and JQUI timepicker + conslidated all vendor styling overrides/extensions

studio - resolving a bug where JQUI sets the z-index of our datepickers to 1, which is less than our dynamic tooltips, causing visual display/access issues.