Fix NPE in Frame#add method.

Adding a frame into a new frame caused NPE since _names field was null.
Refactoring to extract CM adaptation code from GBM/DRF to ValidationJob.

Fix includes:
 - Job#exec is private defining strategy compose of calling execImpl and
   cleanup
 - each job can define cleanup stage
 - ValidatioJob now computes all required information for CM adaptation
Merge remote-tracking branch 'origin/master' into mm_cm_fix
Merge remote-tracking branch 'origin/master' into mm_cm_fix
Removed assertion from Job.

GLM2 does not handle "classification" flag since it has a distribution
parameter.
Fix a typo in R-runner.
Missing check for regression.
Merge remote-tracking branch 'origin/master' into mm_cm_fix