#2119 Add IndexFeatures to CustomKernel and add document.
Added id3 tree pruning
sudoku recognizer notebook add to news
	- accented vowels
changes in decision tree pruning method
Merge pull request #2132 from ahcorde/sudoku_ipythonNotebook

sudoku recognizer notebook add to news
minor change in prune_tree documentation
Merge pull request #2128 from mazumdarparijat/decision_tree

Added id3 tree pruning
Added guard to abort when using the broken function -- to see what will break.
improved gradient descent in CNeuralNetwork
CUAIFile class added to parse and write UAI file format
Adding "is_sorted" method to SGSparseVector for a better sanity check in "sparse_dot".
Added unit tests to detect sparse_dot bug.
Merge pull request #2019 from abinashpanda/develop

Created CUAIFile class (Issue #1913) to save and load file in UAI file format.
Merge pull request #2134 from tklein23/broken_sgsparsevector_sparse_dot

Avoid broken sparse_dot in SGSparseVector - issue #2133
cleanups in CNeuralNetwork
Fix comments and ERROR information.
Merge pull request #2135 from khalednasr/develop

improved gradient descent in NeuralNetwork
Reactivate unit tests.
Fixing sparse_dot() by checking if vectors are sorted (and using expensive fallback if not).
Minor style change.