* fix: R class fields alias
* implemented with clearer approach

As detected by Eclipse, and the test case doesn't depend on the explicit casting.

* Fix missing import for class Generics map.
* Add import only when needed (in non-inner class declaration)
* Remove unneeded import

fix: replace recursive analysis algorithms with iterations to avoid StackOverflow on big methods (#441)

Fix visibility access modifies for methods (see discussions in #370 and #387):
    * all virtual methods become public
    * direct methods become private (instead constructors and static methods for now)
    * such modifications perform by default and can be disabled by the option in preferences (`--respect-bytecode-access-modifiers` in jadx-cli)
    * if changed to method added comment (`Access modifiers changed, original: private`)