* renamed VideoInfoItem to VideoPreviewInfo
* moved streaming service-related classes into their own, new package services
* added javadoc to some classes and methods (where functionality is known well enough to explain)
* De-duplicated common fields between VideoInfo and VideoPreviewInfo by moving them into a common superclass: AbstractVideoInfo
* Removed 2 methods which only call super(), and therefore are unnecessary: PlayVideoActivity.onResume() and PlayVideoActivity.onPostCreate(Bundle)
* still need to use the start position value stored in the PlayVideoActivity's Intent bundle, to set the VideoView using seekTo()
* need to test timestamp extraction regex, and possibly move it somewhere else
*need to find a better way to get the startPosition value to ActionBarHandler, which I thought used VideoInfo objects, but apparently doesn't
* currently there is a small setStartPosition() method
Conflicts:
app/src/main/java/org/schabi/newpipe/VideoItemDetailFragment.java -- still used class-based passing
app/src/main/java/org/schabi/newpipe/VideoItemListActivity.java -- just some whitespace