MEMORIAM: Add recognition for contributors no longer with us

Its sad to have this but as the project ages, also perhaps inevitable.
Besides their contributions, remember them here.

(From OE-Core rev: cd9006b20281cef0051ed60a2cfee8c809c24f76)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

MEMORIAM

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+Some project contributors who are sadly no longer with us:
+
+Greg Gilbert (treke) - Ahead of his time with licensing
+Thomas Wood (thos) - Creator of the original sato
+Scott Rifenbark (scottrif) - Our long standing techwriter whose words live on