Add unity support and update version

[sergio-costas]

Pull Request Template

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of change

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• [X] General Maintenance
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

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Test Configuration:

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Checklist:

• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have checked my code and corrected any misspellings

[sergio-costas]

@seb128 This patch should fix https://github.com/ubuntu/gnome-sdk/issues/155

BTW: I tried to "cut" the build-environment line, but it seems that snapcraft refuses to accept the ">" trick.