Add intention for replacing explicit function literal parameter with 'it'

Kotlin's function literals have a shortcut for one-argument literals:
the single argument doesn't need to be explicitly named, but can be
referred via the 'it' contextual keyword.

For example, 'array(1, 2, 3).filter { x -> x % 2 == 0 }'
          -> 'array(1, 2, 3).filter { it % 2 == 0 }'

Add an intention action for this transformation.

generators/src/org/jetbrains/jet/generators/tests/GenerateTests.kt

@@ -369,6 +369,7 @@ fun main(args: Array<String>) {
             model("intentions/insertCurlyBracestsToTemplate", testMethod = "doTestInsertCurlyToTemplate")
             model("intentions/moveLambdaInsideParentheses", testMethod = "doTestMoveLambdaInsideParentheses")
             model("intentions/moveLambdaOutsideParentheses", testMethod = "doTestMoveLambdaOutsideParentheses")
+            model("intentions/replaceExplicitFunctionLiteralParamWithIt", testMethod = "doTestReplaceExplicitFunctionLiteralParamWithIt")
         }
 
         testClass(javaClass<AbstractHierarchyTest>()) {