Add "vertical" dots page indicator to show planet navigation #8
Description
To achieve horizontal navigation between the different planets while having their corresponding moons above them (and hence more intuitive as the solar system is often represented with a relatively horizontal orbital plane), we rotate the obligate vertical GridViewPager view 270 degrees; up/down swipes become left/right swipes, flipping the planets into the familiar horizontal orbital plane.
Android's DotsPageIndicator thus currently shows navigation within a planetary system only (e.g., Mars - Phobos - Deimos). We need a vertical page indicator to show the intraplanet navigation (Earth - Mars - Jupiter) and, lo and behold... DotsPageIndicatorVertical.
Unfortunately, did not succeed to include this new dependency as jar, aar or url, so filed zhoulujue/DotsPageIndicatorVertical#1 and moving on to #10 in the mean time. Will revisit upon activity on the former or completion of the latter.
Heed dev note: There may be conflicts between DotsPageIndicator and DotsPageIndicatorVertical as Android's indicator currently steals the adapter's page scroll listeners.