wip, color grid shader support

src/mol-geo/geometry/color-data.ts

src/mol-gl/renderable/schema.ts

src/mol-gl/renderer.ts

src/mol-gl/shader/chunks/assign-color-varying.glsl.ts

src/mol-gl/shader/chunks/assign-position.glsl.ts

src/mol-gl/shader/chunks/color-vert-params.glsl.ts

src/mol-gl/shader/chunks/common.glsl.ts

src/mol-gl/shader/mesh.vert.ts

src/mol-gl/webgl/render-target.ts

src/mol-gl/webgl/texture.ts