Blender Git Loki

Fix incomplete info for operation keys.

Operations are stored by name keys (multiple operations of the same type
can exist in the same component, currently e.g. in rigid body components
using multiple world build/sync operations). To keep name strings
manageable for now use string constants for the existing operations,
instead of literals used only in the build methods (compiler then helps
avoid mismatches).

Every operation type is also directly associated to a specific component
type. This was previously done only implicitly via the add_to_graph
functions. Now the associated component type is directly accessible from
node factory type information, so we can use a simple id+operation name
key when building the graph, and don't need hidden factorization inside
the graph->find_node method (deprecated code to be removed later).