docs: mender server split license sections

[oldgiova]

Added two new sections to the Open Souce licenses chapter: Mender Server and Mender Server Enterprise, because we had now split them, so we want to maintain them independently

Ticket: QA-820
Changelog: None

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Description

Added two new sections to the Open Souce licenses chapter: Mender Server and Mender Server Enterprise, because we had now split them, so we want to maintain them independently

[lluiscampos]

These are huge files. Consider adding them empty until we have the real content from these components.

[oldgiova]

These are huge files. Consider adding them empty until we have the real content from these components.

I considered it, but to me it could be a legal infringement.. So to be 100% sure, I'd prefer to have them cloned until the next release.