Fix json in ept.json

[pierotofy]

Hey all ✋

I fixed a problem with the ept.json generation code:

• .01 is not a valid JSON number (although it's a valid javascript expression)
• All objects need a key; in this case wkt was missing.
• The wkt string was being double escaped.

(Before, not valid JSON)

"srs": {
"PROJCS[\\\"WGS 84 / UTM zone 15N\\\",GEOGCS[\\\"WGS 84\\\",DATUM[\\\"WGS_1984\\\",SPHEROID[\\\"WGS 84\\\",6378137,298.257223563,AUTHORITY[\\\"EPSG\\\",\\\"7030\\\"]],AUTHORITY[\\\"EPSG\\\",\\\"6326\\\"]],PRIMEM[\\\"Greenwich\\\",0,AUTHORITY[\\\"EPSG\\\",\\\"8901\\\"]],UNIT[\\\"degree\\\",0.0174532925199433,AUTHORITY[\\\"EPSG\\\",\\\"9122\\\"]],AUTHORITY[\\\"EPSG\\\",\\\"4326\\\"]],PROJECTION[\\\"Transverse_Mercator\\\"],PARAMETER[\\\"latitude_of_origin\\\",0],PARAMETER[\\\"central_meridian\\\",-93],PARAMETER[\\\"scale_factor\\\",0.9996],PARAMETER[\\\"false_easting\\\",500000],PARAMETER[\\\"false_northing\\\",0],UNIT[\\\"metre\\\",1,AUTHORITY[\\\"EPSG\\\",\\\"9001\\\"]],AXIS[\\\"Easting\\\",EAST],AXIS[\\\"Northing\\\",NORTH],AUTHORITY[\\\"EPSG\\\",\\\"32615\\\"]]"
}

After:

"srs": {
"wkt": "PROJCS[\"WGS 84 / UTM zone 15N\",GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AUTHORITY[\"EPSG\",\"4326\"]],PROJECTION[\"Transverse_Mercator\"],PARAMETER[\"latitude_of_origin\",0],PARAMETER[\"central_meridian\",-93],PARAMETER[\"scale_factor\",0.9996],PARAMETER[\"false_easting\",500000],PARAMETER[\"false_northing\",0],UNIT[\"metre\",1,AUTHORITY[\"EPSG\",\"9001\"]],AXIS[\"Easting\",EAST],AXIS[\"Northing\",NORTH],AUTHORITY[\"EPSG\",\"32615\"]]"
}

Also noticed that entwine has two additional objects in the srs object:

    "authority": "EPSG",
    "horizontal": "32615",

It doesn't seem to affect potree rendering, but thought I'd point out the difference (perhaps it's a problem, perhaps not).