Added block expansion

The expansion process follows pointers and library links to construct
the full set of actually-used data blocks. This set consists of all data
blocks in the initial blend file, and all *actually linked-to* data
blocks in linked blend files.

I've also removed non-recursive dependency listing.

blender_asset_tracer/cdefs.py

@@ -55,4 +55,5 @@ PTCACHE_EXT = b'.bphys'
 PTCACHE_PATH = b'blendcache_'
 
 # BKE_node.h
+SH_NODE_TEX_IMAGE = 143
 CMP_NODE_R_LAYERS = 221