Revert "Revert "remove NewIfChange and other fixes""

This reverts commit f271f72c2cdb38e70823e8ab5bcb0d6ca1efc11d.

Conflicts:
	Signum.Utilities/ExpressionTrees/ExpressionHelper.cs
fix NewIfChange -> Visit
Merge branch 'master' of https://github.com/signumsoftware/framework