Extend and cleanup the VMX to domain XML mapping. Add the domain XML to
VMX mapping functions.

* src/esx/esx_driver.c: add esxDomainXMLToNative()
* src/esx/esx_vmx.[ch]: add esxVMX_SCSIDiskNameToControllerAndID(),
  esxVMX_IDEDiskNameToControllerAndID(), esxVMX_FloppyDiskNameToController(),
  esxVMX_GatherSCSIControllers(), add basic handling for the VMX guestOS entry
  to distinguish between i686 and x86_64, make SCSI virtualDev VMX entry
  optional as it should be, map the VMX networkName entry to the domain XML
  interface bridge name, add basic mapping for serial devices in pipe mode,
  add several esxVMX_Format*() functions