Create types that resemble basic_interpreted_path and basic_path_builder that allow easier batching of all 2D graphics operations

[mikebmcl]

While there's nothing per se that currently blocks batching operations, it would be much easier to do batching with a container type that holds a variant of all 2D graphics operations (thus allowing users to build and modify a series of 2D graphics operations) and a class type that is an immutable set of 2D graphics operations (which can be more easily optimized into a command list by back ends that take advantage of hardware acceleration using current graphics acceleration technology).