Makefile to unregister the component

[nicmcd]

make all (the default) includes installing (aka registering) the component with SST. However, make clean does not unregister the component. I suggest one of the two following options:

1. Include the sst-register -u calls directly in the clean target.
2. Include a new target called uninstall that has the sst-register -u calls. This would probably infer a target called make clean-all that performs clean and uninstall.

If you agree and tell me what you want, I'd be glad to create a PR for you.