Changed `PlugReference` to `PlugsReference` #352

Job	Run time
build	5m 57s
test (BoxingTests.Kernel)	1m 48s
test (Cosmos.Compiler.Tests.TypeSystem.Kernel)	2m 20s
test (Cosmos.Compiler.Tests.Bcl.Kernel)	2m 55s
test (Cosmos.Compiler.Tests.Bcl.System.Kernel)	3m 36s
test (Cosmos.Compiler.Tests.Exceptions.Kernel)	1m 49s
test (Cosmos.Compiler.Tests.MethodTests.Kernel)	1m 49s
test (Cosmos.Compiler.Tests.SingleEchoTest.Kernel)	1m 45s
test (Cosmos.Kernel.Tests.Fat.Kernel)	3m 6s
test (Cosmos.Kernel.Tests.IO.Kernel)	1m 51s
test (SimpleStructsAndArraysTest.Kernel)	1m 54s
test (Cosmos.Kernel.Tests.DiskManager.Kernel)	1m 50s
test (GraphicTest.Kernel)	2m 11s
test (NetworkTest.Kernel)	54s
test (AudioTests.Kernel)	4m 1s
test (MemoryOperationsTest.Kernel)	1m 58s
test (ProcessorTests.Kernel)	1m 40s
	41m 24s

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