Based on discussions in #2212.
Minimal invasive changes to the Factorization objects for 0.1.
All existing functionality is retained,	with only a few	renamings for clarity.

Replaces the *d routines with *fact routines:
         lud ->lufact
         chold -> cholfact
         cholpd-> cholpfact
         qrd ->qrfact
         qrpd -> qrpfact

Replaces * and Ac_mul_B on QRDense objects:
         qmulQR performs Q*A
         qTmulQR performs Q'*A

Updates to exports, documentation, tests, and deprecations.

This is a self-contained commit that can be reverted if necessary
close #2062