internal separation of glimmaMDS, glimmaXY

[hasaru-k]

• code/functions for glimmaMDS and glimmaXY/glimmaMA are entangled in the same javascript widget file and in the same R file
• poor extensibility
• MDS plot is significantly slowed down by having to load datatables library which it does not use
• hard to decipher the javascript file because it generates two different widgets Separating out the widget into a separate widget for MDS plots and a separate widget for MA/XY plots will address these issues, in the same style as networkD3.