message: document the new sphere params
diff: @@ -656,9 +656,9 @@ representations in the application this geometry allows a flexible way
  of specifying the data of center position and radius within a [data]
  array:
  - ---------- ----------------- -------- ---------------------------------------
  + ------------ ----------------- ----------------------- ---------------------------------------
  Type Name Default Description
  - ---------- ----------------- -------- ---------------------------------------
  + ------------ ----------------- ----------------------- ---------------------------------------
  float radius 0.01 radius of all spheres
  (if `offset_radius` is not used)
  @@ -675,15 +675,35 @@ array:
  int offset_radius -1 offset (in bytes) of each sphere's
  "float radius" within the `spheres`
  + array (`-1` means disabled and use `radius`)
  +
  + int offset_colorID -1 offset (in bytes) of each sphere's
  + "int colorID" within the `spheres`
  array (`-1` means disabled and use
  - `radius`)
  + the shared material color)
  vec4f[] / color NULL [data] array of colors (RGBA/RGB),
  - vec3f(a)[] color is constant for each sphere
  + vec3f(a)[] / color is constant for each sphere
  + vec4uc
  +
  + int color_offset 0 offset (in bytes) to the start of
  + the color data in `color`
  +
  + int color_format `color.data_type` the format of the color data.
  + Can be one of:
  + `OSP_FLOAT4`, `OSP_FLOAT3`,
  + `OSP_FLOAT3A` or `OSP_UCHAR4`. Defaults
  + to the type of data in `color`
  +
  + int color_stride `sizeof(color_format)` stride (in bytes) between each color
  + element in the `color` array.
  + Defaults to the size of a single
  + element of type `color_format`
  +
  vec2f[] texcoord NULL [data] array of texture coordinates,
  coordinate is constant for each sphere
  - ---------- ----------------- -------- ---------------------------------------
  + ---------- ----------------- ------------------------- ---------------------------------------
  : Parameters defining a spheres geometry.
  ### Cylinders
  