S3g protocol receiver

Testbench included. To run testbench do:

cd build
echo verilog work ../src/top.v >fuse.src
echo verilog work ../tb/s3g_rx_tb.v >>fuse.src
fuse -prj fuse.src -o top_exe work.s3g_rx_tb
./top_exe -gui -view ../tb/s3g_rx_tb.wcfg

For iterative change and test, just edit sources, rerun fuse command
and press Relaunch button in gui