Documentation on package

## Documentation of package deducorrect

Van der Loo, De Jonge and Scholtus (2011):
  Correction of rounding, typing, and sign errors with the deducorrect package. Discussion paper 201119 of Statistics Netherlands.
Van der Loo and De Jonge (2011):
  Deductive imputation with the deducorrect package. Discussion paper 201126 of Statistics Netherlands.
Scholtus (2008):
  Algorithms for correcting obvious inconsistencies and rounding errors in business data
Scholtus (2009):
  Automatic correction of simple typing error in numerical data with balance edits
Pannekoek (2006):
  Regression imputation with linear equality constraints on the variables. (external link to free paper).
git repository
  Git repository of the code on Google code.