SPICE kernel furnishing decorator

[subagonsouth]

Algorithm Description:

Implement a decorator that will handle the furnishing of spice kernels. Base this on EMUS but strip out the SPICE API code. This will start fairly basic to just furnish spice metakernel/kernels that we have.

Also implement a decorator that will set the environment variable to point to the test SPICE metakernel that we have from Nick.