Make Charts API Example module use plugins, since the render files were deleted. Now more closely resembles Charts Blocks.

Removed render classes in favor of plugins, which had taken over the functionality already. Also renamed the plugins to be more consistent.

c3 plugin name was not consistent with the renderer and was preventing c3 charts blocks from showing

Issue #2926078 by lbaran: Charts API Example has issue with ModuleHandler.php and issue #2926077 by lbaran: In Default chart configuration, get AttachedAssets.php notice. Also includes misc. changes to HighchartsChartsRender by andieco

start making charts more accessible by adding in three libraries for exporting data and viewing it as a table