import lates changes from math development branch

(from rev 26842) 

The main changes are: 
- add support for drawing Scan and Contour plot from FitPanel
- improve Minimizer interface by adding methods for contours and scan.  
  implement them using Minuit  and Minuit2

Mathcore: 
- improve Fitter class
  mantain now after fitting a reference to the Minimizer and Objective funciton which can be used later for performing the contour and scans      
  - avoid a copy of FitResult class 
 - add new methods in Minimizer for re-setting the variable values 
 - fix the bin fitting using the bin function integral in combination with the gradient or with Fumili 
 - add dictionary for Fit method functions 


Minuit2: 
 remove limit on number of scan points 
 implement scan and contour in Minuit2Minimizer

Minuit
 implement scan and contour in TMinuitMinimizer

SMatrix: 

 Change implementation of SMatrix::Invert (and Inverse) to use the 
 direct Cramer method only for 2x2 (not up to 5x5)
 Add SMatrix::InvertFast using Cramer method up to 5x5 
 (this is having now same behavior as before)

hist: 
 TBackCompFitter: 
 improve class due to change in Fitter. Use now the minimizer reference and 
 there is no need to re-create it
  Add interface for scan and contour in TBackCompFitter
 Add methods to retrieve FitResult and FitConfig

mathmore
 fix a memory leak
 implement changes in Minimizer 

fitpanel
 new dialog for the advanced drawing option with two tabs one for 
 drawing contour the other for drawing scan plots
  fixed some meory leaks and other small problems


git-svn-id: http://root.cern.ch/svn/root/trunk@26866 27541ba8-7e3a-0410-8455-c3a389f83636