adds script timings

also reflects modularization of cv.R into cv_setup.R cv_lrm.R, cv_ols.R and cv.R
modularizes cross-validation procedure

cv.R takes too long to run on its own. Splits setup, lrm, ols, and
collection into seperate scripts
edits applied to manuscript

adds data appendix, multiple imputation writeup, improvements to random
forest section, numerous smaller edits