`bitmap` and `mesh` blocks

[struffel]

To help clients better understand the data they can expect to receive within components, two new blocks should be added.

bitmap

Indicates that the component represents a bitmap with the following properties:

• width: Width in pixels
• height: Height in pixels
• bpc: Bits per channel
• mode: One of grayscale,RGB,RGBA
• colorspace: Open Question: Is there an existing list of common color spaces that could be used here?

mesh

• faces: Number of faces
• up_axis: One of +x,-x,+y,-y,+z,-z Open question: Should this be defined here or individually for every format like it is currently happening with the format.obj datablock? The problem with defining it here is that some formats actually prescribe a specific up-axis so this field would be in conflict.