Improve new Sirius project template

[dvojtise]

In complement to #117
Many improvements may be done either in the current template or in new templates (this can be part of exercises given to student 😉 )

Some ideas:

• use EOpposite information to merge edges
• use containment information to display black diamond ends
• display containment as nested boxes instead of linked boxes
• wizard allowing to configure individually how a given containment relation must be displayed ( link, link + diamond, nested box)
• use information about existence of xtext editor (that is stored in the .dsl file) in order to automatically add xtext integration like the one in logo crash course (cf. https://github.com/dvojtise/mde-crashcourse-logo/blob/master/part3-mmfirst-solution/fr.inria.sed.logo.design/src/fr/inria/sed/logo/design/Services.java and in the odesign)
• add actions such as creation tool, drag and drop (in the palette and/or in popup in the diagram)
• other Sirius representations (tables ...)
• support of folding
• label based on uriFragment when there is no name attribute
• automatic change of the color of the container depending on the concrete type (instead of only gradient white to light grey)