Import/export from/to JSON

[manolodd]

Define a JSON file format for OpenSimMPLS scenarios (OSM). It wil be necessary to modify classes under simMPLS.io.osm to import/export from/to JSON. I'll use mjson for this.

[manolodd]

Should be good the use of mjson (@bolerio) library that provides also JSON Schema validation capabilities.

https://github.com/bolerio/mjson