Coreboot 4.13 & 15" Boards

This fixes Heads at the moment of upgrade of the majority of boards to coreboot 4.13 and the addition of 15" lenovo boards. There have been too many changes to Heads since 2017 to note here. But this release fixes Heads at a moment where it has working boards for devices we currently have in use in our organization (t520, x230, t430, t530, w530).

This release is an exact copy of is research:heads master on the release date and does not reflect organization-specific changes we make to our boards, which are in eganonoa:heads master and its branches. It is made to provide a point of reference for future debugging because at present osresearch:heads has a rolling release model.