PageStack: remove PageContainer

Change-Id: I22054e490e8e2da71f59d6a61463e440e5fae6b7
better cleanup

Change-Id: I8b99a0f52c09c01ac3f68801d24cd7745b1f55a0
warn about anchors

Change-Id: I0612536ca6d15bfbc239d12a0ea123e76a452ab3
only allow a page to be pushed once

Change-Id: Ic1ea447f40555e99cbaf7a9bc5e06890dc7947d2
allow pushing several times after all

Change-Id: I4923955be31b8b9b6fcfc781918dcb96350fe1cc
wip

Change-Id: I187865eaaa4f94dd4db70a9155f99fb71caca73e
implement cleanupAnimation

Change-Id: I6d8431b928755e49122ab84abf704d24d14abf01
use enter/exit element as transition element

Change-Id: Ibf8e94e5cb5725e8998b71559ffe7491f4de9058
implement userdata

Change-Id: I33719398ed4f40edc32d4fc8e324ca5a5f051d86
internal doc

Change-Id: I40503436d30804edaeb2dfd0b2f6e485864c44f6
skip userdata after all

Change-Id: I2906684ab65b13e8f6a5c7135d1759550942a8ec