Initial setup of the Computer Spoke.

We're adding a new spoke to the node entities.
This spoke is called Computer and it will perform the node's compute
using the input plugs and the node's parameters.

We've added a new BaseParameter and templated Parameter classes.
Currently we're only going to support ints floats and strings.

Also fixed up the failing node graph tests.

Also the factory's builders were tweaked for the input and output plugs
and inputnodeinputplug and outputnodeoutputplugs. They now automatically
add them onto the node.  Before they were added to the node externally.

Python wrappers were also adjusted to reflect this.