CSS, Row Container styling

* CSS; nxs-icon-left and right no longer set dimensions of image
* Row container styling is now more generically implemented
* Row container styling now enables setting border top and bottom
* Styling; nxs_js_createcssstyling uses templates instead of 2 input
variables
* Added 0.5 factor for border-widths
* Added function that derives the wp size based on factor value (stored
in metadata of context)
* Renamed bottom_margin => margin_bottom (following CSS naming
convention...)
* Property name "image_border_size" is now renamed to
"image_border_width"