This change adds back component output properties. Doing so
requires splitting the RPC interface for creating resources in
half, with an initial RegisterResource which contains all of the
input properties, and a final CompleteResource which optionally
contains any output properties synthesized by the component.
This change adds functions, `pulumi.getProject()` and `pulumi.getStack()`,
to fetch the names of the project and stack, respectively. These can be
handy in generating names, specializing areas of the code, etc.
This fixespulumi/pulumi#429.
