Adds Xml::Node and spawn method to context
Chames Map::Frame to Map::Namespace
Adds `content` and `html` methods to Stencil class and reverses some previous changes
Adds R context and stencil related classes and unit tests
Some changes to the context inteface
Changes Component from being a templated class to a plain class to facilitate specifying inheritance in Python class (and because it was mostly unecessary). Also changes some of the Context method names.
Changes R Context method names
Numerous changes to Python package
Tidies up R macros
Reconfigures package including getting rid of shortcuts.R
Changes to package functions
Make Stencil inherit from Component
Adds Component class to R package
Puts Component static members in separate .cpp file
Minor change to Python Makefile
Add node type methods to Xml::Node
Explivit handling on unforund R methods
Adds Component$log() method in R package
Stencil read, write and commit properly call corresponding base Component methods
Minor change in implementation of Stencil.content()