core: exporting the block registry (for RPC setup).
ctrlport: Changed RPC setup call to only require block's alias and not all of the other info we used to require. gr_top_block shows the new interface.

The flowgraph now automatically calls setup_rpc on every block when the flowgraph is run. No need to have setup_rpc() in the block's constructor.
ctrlport: updated all blocks using controlport to use new style of setup_rpc.

QA fixed and passing.