Try to emulate tox -e type of target/environment.
This works natively in tox.ini as long we have commands to run there
(doesn't support inheritance).
For dox.yml the format has been improved, the format looks now like this :
target1:
images:
commands:
add:
prep:
target2:
images:
commands:
add:
prep:
we still support old format with single target.
Follow up patches in this series improve this implementation.
Change-Id: I2a30aaa63fd4e47fd76f29ed5e5cb025ca326016
af4113abc2