Cherry-Picked the following commits:
0defd8f2 Changed "WebM" to "AOMedia" & "webm" to "aomedia"
54e66767 Replace "VPx" by "AVx"
5082a369 Change "Vpx" to "Avx"
7df44f17 Replace "Vp9" w/ "Av1"
967f722f Remove kVp9CodecId
828f30ce Change "Vp8" to "AOM"
030b5ffc AUTHORS regenerated
2524caee Add ref-mv experimental flag
016762be Change copyright notice to AOMedia form
81e55269 Replace vp9 w/ av1
9b94565b Add missing files
fa8ca9f2 Change "vp9" to "av1"
ec838b76  Convert "vp8" to "aom"
80edfa01 Change "VP9" to "AV1"
d1a11fb9 Change "vp8" to "aom"
7b582513 Point to WebM test data
dd1a5c8d Replace "VP8" with "AOM"
ff00fc0f Change "VPX" to "AOM"
01dee0bb Change "vp10" to "av1" in source code
cebe6f0c Convert "vpx" to "aom"
17b05679 rename vp10*.mk to av1_*.mk
fe5f8a8a rename files vp10_* to av1_*

Change-Id: I6fc3d18eb11fc171e46140c836ad5339cf6c9419