Additional button/icon coloring

[lat9]

As noted in #211 by @dennisns7d, the checkout-related buttons should have their own coloring, to help guide a customer through the checkout process

• button_continue_checkout
• button_confirm_order

The quick-reorder sidebox's .fa-cart-plus icon should use the same coloring as the "add-to-cart" button.

In addition, reviewing the current /includes/templates/bootstrap/css/stylesheet_colors.css, additional color configurations should be added for the various carousel elements:

• a.carousel-control-prev, a.carousel-control-next
• a.carousel-control-prev:hover, a.carousel-control-next:hover
• .banner-carousel .carousel-indicators li

Those changes will get all current elements out of the stylesheet_colors.css.

[lat9]

Note that as a result of this and the other updates identified in #211, the previously distributed /css/stylesheet_colors.css is no longer needed and will be removed from the distribution. All styling in the as-distributed version of that file are now overridden by the /css/zca_bootstrap_colors.php's processing, since that file's the last loaded from the /css sub-directory.

Noting that the following is not needed, since the css/site_specific_styles.css already provides that functionality!

That module's processing will be updated to, if present, load a /css/zca_bootstrap_stylesheet.css file which will enable a site to provide any styling overrides needed.

[lat9]

Noting that much of these changes is now documented in the template's wiki: https://github.com/lat9/ZCA-Bootstrap-Template/wiki/ZCA-Bootstrap-Stylesheets-and-Colors