Android native stack bugfixes. (#190)

A few bugs fixed with android native stack in this commit:
 - fixed a problem with views not resizing when keyboard appears, the bug was due to onMeasure forwardin getHeight which was the old height of the container instead of the changed one
 - fixed a problem with back button behavior not being consistent. Now back button is controlled by 'gestureEnabled' to emulate iOS behavior where there is no hw back button but you can swipe back instead.
 - added compatibility for "contained" modal styles - for now we always render "containted" fragments on Android, plan to add a way to render in dialogs in the future

android/src/main/java/com/swmansion/rnscreens/ScreenStackHeaderConfigViewManager.java

@@ -82,6 +82,11 @@ public class ScreenStackHeaderConfigViewManager extends ViewGroupManager<ScreenS
     config.setHideShadow(hideShadow);
   }
 
+  @ReactProp(name = "gestureEnabled", defaultBoolean = true)
+  public void setGestureEnabled(ScreenStackHeaderConfig config, boolean gestureEnabled) {
+    config.setGestureEnabled(gestureEnabled);
+  }
+
   @ReactProp(name = "hideBackButton")
   public void setHideBackButton(ScreenStackHeaderConfig config, boolean hideBackButton) {
     config.setHideBackButton(hideBackButton);