allow saving simulation state from the gui (trac #2513)

[behrisch]

Migrated from http://sumo.dlr.de/ticket/2513

{
    "status": "new", 
    "changetime": "2016-10-14T11:05:42Z", 
    "description": "", 
    "reporter": "namdre", 
    "cc": "", 
    "resolution": "", 
    "_ts": "1476443142921085", 
    "component": "simulation gui (GUISIM)", 
    "summary": "allow saving simulation state from the gui", 
    "priority": "major", 
    "keywords": "", 
    "time": "2016-07-28T07:02:29Z", 
    "milestone": "1.0.0", 
    "owner": "", 
    "type": "enhancement"
}

[behrisch]

@behrisch changed milestone from "0.28.0" to "0.29.0"