A couple of speedups to the multivariable regression code,
and stub out architecture for actually doing it.

Also I removed the "n = " line that Daniel was unsure about; if this causes a bug, all blame is on me.
rmultivariableregression, for use as a test benchmark
actually make the last commit run
Make rmultivariableregression return what it is supposed to

Also hack around a bad corner case that you'd only stumble into when testing this very function.
hack around numerical instability
Tighten comments and readability

Also, found a chance for backsolve I missed last time.
Put the dist'n constants in from the paper
Merge branch 'master' of https://github.com/Daniel306/stat440

Conflicts:
	R/MultivariableRegression.R
I overrode most changes, but took the MNIW.Mu formula change.
Incorporate flat priors (by default) to lm.multivariable()

plus:
* Repair the bug I indeed introduced by removing 'n'.
* Be overly clever: use mahalanobis() instead of the formula as written
* Comments
Runnable Multivariable Regression Example

To use: uncomment the very last line.
TODO: checkpoint progress
add sd vector and merged all reps into one