A Phase II Clinical Trial for Untreated Patients with Multiple Myeloma Eligible for Stem Cell Transplant: Lenalidomide (Revlimid®) plus Low-dose Dexamethasone (Ld x 4 cycles) Then Stem Cell Collection Followed by Randomization to Continued Ld or Stem Cell Transplantation (SCT) Plus Maintenance Ld for SCT Patients Not Achieving at least a Very Good Partial Response (VGPR) or Having High-risk Disease