Support Xilinx and Altera Simulation

[mattfel1]

For users who have license for these because they purchased an fpga from the vendor, and don't necessarily have access to vcs

[raghup17]

Do we need ISE? The boards supported in Spatial should come with a Vivado license with their purchase. Would supporting the Vivado simulator suffice?

[mattfel1]

Yea no particular reason I chose ISE, I just mean to support some way that a Xilinx person can simulate