Moved low-level node-finding code over to depsgraph_query.c
Various comment fixes for dividers
Skeleton DEG_get_node_*() API functions for getting nodes when we only know RNA Pointers
Stub for API method to look up appropriate node querying conditions given just Pointer+Prop
Stub for function to figure out query conditions given rna pointer

Currently, this just defines the default return values, in absence of
any additional handling which may arise if we find anything interesting.
Hook up DEG_get_node_from_pointer() logic
Special handling for bones (when doing RNA lookups)