For mpd codes, rename dash_packager to edash_packager; for media codes,
add namespace edash_packager.
Change-Id: I1120e6110c734cd02bdbe15f1cf7abddcdfdd7ea
XML compare function for comparing a subset of MPD or the whole MPD.
The children must appear in the same order but the order of attributes
do not matter.
Change existing tests to use XmlEqual() instead of string comparison.
Change-Id: Ib7f80f52b5bed5b5f7c2517620c8955261a4b6a2