Make it possible to lock runner on a specific project

Make it possible to lock runner on a specific project.

![Screen_Shot_2016-06-20_at_4.03.08_PM](/uploads/186378643a20106ff0b67b6fd8bd7f28/Screen_Shot_2016-06-20_at_4.03.08_PM.png)

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![Screen_Shot_2016-06-20_at_9.54.52_PM](/uploads/c479abdffaf19f383bb6b5a42bdd6cc3/Screen_Shot_2016-06-20_at_9.54.52_PM.png)

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![Screen_Shot_2016-06-20_at_9.56.26_PM](/uploads/6ad838679b0c28a1fe2e20e9224387ea/Screen_Shot_2016-06-20_at_9.56.26_PM.png)

Closes #3407

See merge request !4093