Call for testing current UEFI experimental support

I see the current state of feature/uefi as good enough for a broad call for testing. If the results are good enough (i.e. not too many identified hardware support regressions, to balance with the huge benefits that we already know about), then I’ll propose we include this support, as a technology preview, in Tails 1.1.

Parent Task: #5739 (closed)

Original created by @intrigeri on 7059 (Redmine)