[ENHANCEMENT] Cleanup DataCube API

[mmebsout]

The DataCube API is complicated for nothing and more often than not, a lot of informations returned aren't needed.
for example if one needs only the information for one metadata (option witch by the way isn't used by DataCube) he should use a url like this one :

/localhost:8081/cubeExplorer/rest/header?entry=1342228703_M17-2_SPIRE-FTS_15.0.3244_HR_SLW_gridding_cube.fits &metadata=NAXIS1

and would get this as an answer :

{
    "response":{
        "feature":{
            "geometry":{
                "coordinates":[0,0],
                "type":"Point" 
                },
                "type":"Feature",
                "properties":{
                    "metadata":[["NAXIS1","12","size of the n'th axis"]], // the information needed is here
                    "fileType":"fits",
                    "dimensions":{
                        "typeVal":"Value",
                        "typeY":"DEC--TAN",
                        "stepZ":0.29979246854782104,
                        "typeX":"RA---TAN",
                        "stepX":-0.004861111287027597,
                        "stepY":0.004861111287027597,
                        "refLat":"-16.216666666666665",
                        "unitX":"deg",
                        "refX":"6.0",
                        "unitY":"deg",
                        "unitZ":"GHz",
                        "refZ":"953.0",
                        "refY":"8.0",
                        "unitVal":"W m-2 Hz-1 sr-1",
                        "refLevel":"732.39297489",
                        "typeZ":"Frequency",
                        "dimZ":1905,
                        "dimY":15,
                        "dimX":12,
                        "refLon":"275.0937083333333" 
                    }
                }
            }
    },
        "status":"OK" 
}