templatekw: add helper method to generate a template keyword for a namespace This marks our second feature of the namespace api: automatic template keyword. This patch adds a method that takes in a namespace and uses the node-to-name map to output the list of names.

namespaces: add names method to return list of names for a given node In the previous patch, we added a node-to-name map property. This patch just exposes that interface to the api.

namespaces: add nodemap property This patch adds a node-to-name map property to the namespace. This is necessary because we cannot simply invert the name-to-node map because we do not assume the name-to-node map to be unique (for example, consider named branches: many nodes have one branch name). The node-to-name is helpful in log commands where we are already iterating over a set of nodes and want to display some kind of naming information to the user.