Better support for deprecated methods

PyCharm could benefit from better support for marking methods and classes as deprecated.  

Currently, the only way to do so if if the method emits a DeprecationWarning, resulting in somewhat clunky syntax.  Ideally, a decorator could be written to emit that warning while still having PyCharm detect the use of a deprecated method and mark the usage accordingly in the UI with the strikethrough treatment.  Alternatively, just establishing a convention of detecting the usage of any decorated named "deprecated" would suffice and not require as much complex static analysis.  Thanks!