Handling of non-square `AbstractQ`

[araujoms]

I'm not sure whether this is a bug or intentional, but the handling of non-square AbstractQ is rather inconsistent.

import LinearAlgebra.QRPackedQ
q = QRPackedQ(randn(4,3),randn(3))
size(q) != size(Matrix(q))
size(Matrix(q')) != size(Matrix(q)')
size(Matrix(q')*Matrix(q)) != size(q'*q)
size(Matrix(q)'*Matrix(q)) != size(q'*q)
size(Matrix(q')*Matrix(q)) != size(Matrix(q)'*Matrix(q))
s = QRPackedQ(randn(5,4),randn(4))
size(Matrix(s)*Matrix(q)) != size(s*q)