[PATCH] support for gPXE and esxi5

Two patches, pushed to my github account: https://github.com/jimi1283/cobbler/commits/esxi-improvements The ESXI5 patch requires the gpxe patch, since the only sane way to add the support for it to cobbler was via the gpxe process documented in the VMware build guide. This allows all of the files to be served via httpd, otherwise you have to copy the entire ISO contents to a TFTP directory (which required some ugly hacking in cobbler). The one caveat about the gpxe process is that you must manually copy the undionly.kpxe file to your tftp directory. Newer distros package the etherboot files, otherwise you'll have to download the files from http://etherboot.org/wiki/download and build the file yourself (it's a fairly painless process). Another TODO is to make the same setup changes for DNSMASQ, right now this only supports ISC DHCPD. There is a new setting called enable_gpxe, which is used currently only when new items are created. There is also a new field for systems and profiles by the same name, which sets it on a per-object basis. This isn't being used for profiles yet, nor will it work on systems without an interface and MAC specified, but when enabled on a system with a MAC it will create an entry in dhcpd.conf that is configured to chain load the undionly.kpxe file. I plan on adding support for generic profiles and systems without a MAC, but it might be a some-what convoluted process and I'm trying to work out the best way to do it (currently it'd involve chain loading gpxe, and then detecting that you don't want to use gpxe and chain loading back into the old pxelinux.0 file). I plan on merging these into master in the near future unless people have major issues during testing. Enjoy!