Exponential function
Remove ///// lines
Implemenation details
Docs for methods of Univariate and Bivariate
added log and diff for / operator
a few Tests for exp and log
Cancellation method for addition
Refactor the expand code from Simplify to CTerm
Refactor cancel methode code
Part 1 of rewrite of functions
mulZero rewrite
Part 3 - rewrite of functions

Cleaned up flatten, delIdentity. GroupNegative now works as it is intended.
groupDivide and cancelDiv; simplified singleTerm
Improved simplifyTerm (previously singleTerm)
Added add method
Minor change to add
Completed implementation of opSimp
Deleted groupMutliple and cancel
Minor improvements to opSimp
Documentation to Expression.scala