New layout of the nmaas.eu page

As briefly discussed with @korvoj, nmaas.eu requires a new layout (now when no nmaas Portal is behind it).

Pointers:

• This new static webpage can follow the design of vLAB and vNOC docs pages
• It need to contain:
  • references to running nmaas instances (Portals) along with a paragraph on text describing the "purpose" of given instance
  • references to dedicated use-case doc pages (vNOC, vLAB)
  • central documentation

@korvoj any comments are welcome