Add support for svgo options about dr-svg-sprites

[phloe]

Merged this.

[gregori-goossens]

just for sharing my current "no altering" svgo options:

"svg-sprites": {
      options : {
        svgo: {
          plugins: [
                { removeViewBox: false },
                { cleanupIDs : {
                    remove: true,
                    minify: false
                }},
                { removeUselessStrokeAndFill: false },
                { moveGroupAttrsToElems: false },
                { collapseGroups: false },
                { convertPathData: {
                      applyTransforms: false,
                      straightCurves: false
                 }}
          ]
        }
      },

NB : cleanupIDs.minify : false prevent renamed id and reduce conflict on id when mege svg into sprite. (for exemple when you have clipPath tag)

[phloe]

Those options might be nice upgrades to the options.svgo defaults - I'll add them :)