Fletcher AWS F1 platform support

Before running any other command, source sourceme.sh. This will do everything needed to set up the AWS SDK and HDK. It will also clone the subrepos if you haven't already.

After that, you'll probably want to build and install the hardware and/or cosimulation runtime library in the runtime directory. This allows you to use the aws and aws_sim Fletcher platforms.

In order to run synthesis and get started quickly with host application development, you can use the project-generate.sh script. Given a VHDL directory generated by Fletchgen, it'll generate everything you need to get started. The skeleton project includes a readme file with further information.