Define base Brillo partitions.

This introduces the basic partitions expected to be available on any
Brillo system, including boot{_a, _b}, system{_a, _b}, odm{_a, _b},
misc, and userdata. Board- or application-specific .bpt files can
override as needed.

TEST=Manually, verified that partition-table.{img, bpt} is generated.
BUG=27831397

Change-Id: I396bf3f9298b8a7a9c7fb1dac5398d0ea1ecd043
2 files changed