How to construct nodes?

[stonier]

Right now, I'm adopting the following convention:

• node_name and namespace in via __init__()
• rclpy.create_node(node_name=..., namespace=..., ...) in setup()

There is a constraint to this though - it assumes that all behaviour nodes run off the default context. Is there ever a situation in which someone would want to specify the context as well?

If so, then we'd need to pass in the node itself via setup(). This would require py_trees change to setup() so that it could take in an arbitrary dictionary of arguments that behaviours could cherrypick from.

[stonier]

Haven't yet found a reason to need a non-default context.

[stonier]

Reverting back to the one node rules them all. See #72 for details.