Replace Browser with Browser2 and BookmarkProvider

Browser is going away. Browser2 is a tiny, WebView-based browser for
testing purposes. BookmarkProvider will take over the
"com.android.browser;browser" authorities and return empty Cursors for
all queries. See packages/apps/Browser2/README for how to obtain a
regular browser.

BUG:19351071
Change-Id: I8af605ec65a1185923598ba553a98e3fd9b887db