Detailed Description

The current version of the frontend api only allows setting the mesh / segment color via api.data.setSegmentColor(segmentId, color);. But the new transparency feature for meshes is not exposed.
Thus, adding a new third optional parameter setting the alpha value of the mesh would be helpful.

Context

• Specific to long-running jobs (set jobsEnabled=true in application.conf)
• Specific to webknossos.org (set isDemoInstance=true in application.conf)
  See here