Added two flags to the frame header:
intra_only:
Signals that the frame is encoded using only INTRA
coding modes.
reset_frame_context:
Indicates that the coding context specified
in the frame header should be reset to default values before the
frame is encoded/decoded.
Change-Id: I182d46f1f84fb67a13c46ad767f246a38d7861a2
9e5bb9598c