JSMF Model comparison

[jssottet]

JSMF model comparison (model difference)
It would help in defining the highlight of difference between two sunbursts #1

[jssottet]

• add metrics of comparison (some are working = number of classes),
  add the number difference for attributes....

[jssottet]

Make a diff metamodel that describes links of source and target models (currently it is only a JS object containing source, target model elements and the differences)