RSRP-455641: Respect "using static" clauses in refactoring

C#6 introduces the Java-like "using static" clause which can make code a lot cleaner. Consider (using my RandomGenerators Nuget package):

using PeanutButter.RandomGenerators; 
[TestFixture] 
public class TestWibble 
{ 
[Test] 
public void Womble_ShouldNebulizeTheActuator() 
{ 
var name = RandomValueGen.GetRandomString(); 
... // rest of test continues 
} 
}

which can now be written as:

using static PeanutButter.RandomGenerators.RandomValueGen; 
[TestFixture] 
public class TestWibble 
{ 
[Test] 
public void Womble_ShouldNebulizeTheActuator() 
{ 
var name = GetRandomString(); 
... // rest of test continues 
} 
}

Which considerably cleans up test fixtures with lots of tests and lots of randomly generated input (as a very specific example). Now, if I had started this test fixture in another class file and use the Resharper refactoring to move to its own file, I'll find that all my usages of the statically-imported RandomValueGen are replaced with direct usages and my "using static" clause has been replaced with a simpler "using" clause.