Quickfix for INCOMPATIBLE_MODIFIERS.

I've expanded univerio's quickfix (https://github.com/JetBrains/kotlin/pull/176) to allow the user to choose which one of conflicting keywords should be removed (instead of just removing the one under the cursor). However, the code is much more complicated and I'm not sure whether the feature is worth this complication (since I don't think that this quickfix will be frequently used).