Add DSL for deactivating capabilities

[britter]

Add a shortcut notation to adds a rule which negates the effect of a built-in rule. I.e. what you would have to do manually like this now:

dependencies {
    components.withModule(CGlibRule.MODULES[0]) {
        // Ad-hoc rule to revert the effect of 'CGlibRule'
        allVariants {
            withCapabilities {
                removeCapability(CGlibRule.CAPABILITY_GROUP, CGlibRule.CAPABILITY_NAME)
            }
        }
    }
}