DUI: icons dynamo units(logic)

This PR includes additional logic for Units category.
What is interesting - Units have methods like Operators(e.g. +,%,>, etc.), but these methods are overloaded. So, logic was rewritten a little bit. So that, we can use overloaded operators.

# Reviewers
@Benglin,@vmoyseenko, please take a look.
Can we not make this ```fullName``` as a parameter to override the default behavior? You can make the default behavior of this method ```TypedParametersToString``` to call ```NormalizeAsResourceName(FunctionDescriptor.QualifiedName)``` (since we already have a ```FunctionDescriptor```), and if the caller wanted to override this new behavior, then it can supply ```fullName``` parameter. So in ```TypedParametersToString``` method, you can do this:

```cs
// Override the behavior if the caller needs to change the full name.
if (string.IsNullOrEmpty(fullName))
    fullName = NormalizeAsResourceName(FunctionDescriptor.QualifiedName);
```