Ported 'NegateIsExpressionAction'.
Ported 'InvertLogicalExpressionAction'.
Ported 'JoinDeclarationAndAssignmentAction'.
Fixed remove backinig store tests.
Ported 'RemoveRegionAction'.
Unfortunately there is an exception when trying to remove the region
directives from the syntax tree. I assume that this is a roslyn bug.
Fixed 'ReplaceAssignmentWithPostfixExpressionAction'.
Fixed 'ReplaceWithOperatorAssignmentAction'.
Refactored 'ReplaceAssignmentWithPostfixExpressionAction'.
Ported 'ReplaceOperatorAssignmentWithAssignmentAction'.
Refactored 'ReplacePostfixExpressionWithAssignmentAction'.
Ported 'SimplifyIfInLoopsFlowAction'.
Ported 'SimplifyIfFlowAction'.