Proto commits in spotify/klio

These 4 commits are when the Protocol Buffers files have changed:

Commit:0d98d71
Author:Lynn Root

[core] Add Apache License headers as well as a license header check in the `lint` testenv of tox

The documentation is generated from this commit.

Commit:dfc5f36
Author:Lynn Root

[core] Update protobuf for v2 execution modes As well as mark KlioJob.inputs for deprecation - it doesn’t seem like has ever been needed.

Commit:f22aef4
Author:Lynn Root

[core] Update protobuf definition To maintain proper backwards compatibility. Once users have migrated to klio v2, KlioMessage.data.entity_id should be marked as “reserved”.

Commit:790ec67
Author:Lynn Root

Initial commit