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Some changes:
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cvglasso.R: -remove several function which are already in diffnet.r
            -remove screen_cv.glasso; this function is already in diffnet.r,
            however, the default for include.mean=TRUE and trunc.method are
            different
            -two changes in het.cv.glasso (due to change of defaults in
            screen_cv.glasso)

diffnet.r: -change example
           -screen_cv.glasso: output mu, as this output is required for
           het.cv.glasso