Add UEFI Support to Linaro Tools

This is a follow-up session to the Hardware Pack Extensions discussion, focused specifically on UEFI.

The inital session is here -> https://blueprints.launchpad.net/linaro/+spec/linaro-toolchain-q112-hwpack-extensions-1

Hopefully, the delegates had chance to consider the UEFI requirements previously discussed and can help decide the future direction for adding UEFI to the tools.

Topics for discussion will be set by the previous meeting, but currently, items include:

- Should we host multiple variants of UEFI in 1 hwpack?
  eg Versatile Express A5/A9/A15
- Should we host multiple bootloaders in 1 hwpack?
  eg. u-boot and UEFI.
- How do we modify the tools to create a hwpack so that a UEFI binary is included?
  Eg. command line parameters, config files, etc...
- How do we modify the tools to create a disk image with UEFI?
  Eg, one proposal was a command line parameter to linaro-media-create to specifiy the bootloader required: --bootloader = [none, uboot, uefi, all]
  This will also need to add a kernel and initrd in a format suitable for UEFI, i.e. no U-Boot wrapper. (Do we need to worry about flash-kernel?)