WIP - Convert Media Query-based Responsiveness to xBlock Configured "Sizes"

**This work reverts the responsiveness of ORA xblock. Key points include:**

* due to xblocks being placed in various UI, mediaqueries can't be used reliably
* xblocks cannot get information on their parent element's dimensions
* t-shirt-based sizing, based on responsively made media queries, was recommended given these constraints
* sizes include: xs, s, m, l, xl and correspond to sass variables that have been previously used for native media queries
* this is less than idea but needed and causes: gaps in transitions; a manual class to be added to the .xblock classed HTML element; bloat/redundancy in compiled CSS

**TODO: Needed xBlock Architecture Help**
This work requires that one of the planned support classes (.ui-size-xs, .ui-size-s, .ui-size-m, .ui-size-l, .ui-size-xl) be added to the parent .xblock HTML element the xBlock is rendered in. This support class should be based off of configuration settings. This needs to be set up.

**TODO: Other**
Other tasks needed to support this include:

* proof UI with .ui-size-* classes controlling sizes across browsers
* document this within xblock docs/config