3128: Sum/Product Simplification.
Simplification now hooked to simplify.
A bug fixed. Tests updated.
Tests updated.
Code quality improved.
Merge conflicts fixed.
Test failures fixed.
Removed two redundant tests.
Changed the Algorithm.
Simplification is now order independent.
Removed unused imports
Removed redundant If statements.
Method change_index() added for changing index.
Example failures fixed.
Example failures fixed.
Example failures fixed.
Example failures fixed.
change_index() updated. Doctests fixed.
change_index() updated. Doctests fixed.
Implemented similar to Integrals.transforms.