- adaptation asides to be imported from the XML
- updating SplitMongo to handle XBlockAsides (CRUD operations)
- updating Studio to handle XBlockAsides handler calls
- updating xblock/core.js to properly init XBlockAsides JavaScript

The function initializeXBlock() expects a DOM element, and is passed one in most
cases.  However, when adding a new XBlock component in Studio, the function is
passed a jQuery object, which ends up being forwarded to the actual
initialisation function of the XBlock.

SOL-1, SOL-2, SOL-3

[PLAT-217]