Adds support for passing JSON parameters to initialize XBlock
Adds support for passing JSON parameters to initialize XBlock

4eek/XBlock,EDUlib/XBlock,nagyistoce/edx-XBlock,4eek/XBlock,edx-solutions/XBlock,edx-solutions/XBlock,edx/XBlock,mitodl/XBlock,open-craft/XBlock,mitodl/XBlock,edx/XBlock,open-craft/XBlock,nagyistoce/edx-XBlock,EDUlib/XBlock,lovehhf/XBlock,lovehhf/XBlock