Plugin API version from 3.6.0 to 3.7.0
Plugin API version from 3.6.0 to 3.7.0

The API was published as version 3.7.0, because the content should
only be used by plugins for upcoming releases.

Release-Notes: skip
Change-Id: I0fee5b6d63a44ac371922e0f40ef46bb5d9921b2

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