Create Vivado.gitignore

[stephengroat]

For Xilinx Vivado Suite. Sourced from http://www.xilinx.com/support/answers/61232.html and http://www.xilinx.com/Attachment/ar61232.txt

[stephengroat]

Forgot to add some background info. Vivado is Xilinx's replacement ISE. For using git, Vivado has the following guide (http://www.xilinx.com/support/documentation/application_notes/xapp1165.pdf) for properly configuring the project to use version control.

[shiftkey]

Closed in favour of #2885