Create sdk to create sdk's

[chcosta]

We shouldn't have to include 'nearly' identical sdk.props / targets in the source for every package produced in the arcade repo. We should have some sdk that assists with the generation of our sdk / task packages.

[joperezr]

As part of this, we should also make sure we add common SDK logic which will remove any package or framework references to the sdk package. Take a look at #235 (comment) form more info.