Add ulogd function in R

[jcai849]

Still needs some small work to capture keyboard interrupt from R

[s-u]

Thanks, good idea. I think a better way to organize this is to modify src/ulogd/ulogd.c to do the main()/ulogd() split and then add the R API part into a new file in src. That way we don't need to maintain two copies of the same code. Also, please do not include any formatting changes nor superfluous files (like .gitignore).