[Merge] ~rs2009/unity:master into unity:master

[Rudra Saraswat]

mitya57: I've made the required changes (used 3 for the EmptyTrash change).

As for why we switched to 7.6, we believe the number of the changes made in this release justifies a version bump. Since the diff has been truncated here on LP, you'll find all the 7.6 changes here (especially in the 'release Unity 7.6.0' commit): https://gitlab.com/ubuntu-unity/unity/unity/-/commits/, and here are the complete release notes: https://unity.ubuntuunity.org/blog/unity-7.6/

I've added '-' before the tests command in debian/rules, to ignore the error code.
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https://code.launchpad.net/~rs2009/unity/+git/unity/+merge/429299
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