Implements a comprehensive TestSuite for the Queue plugin. (#180) #351

Job	Run time
cs-stan / Coding Standard & Static Analysis	38s
testsuite / testsuite-linux (8.2, sqlite, lowest, false)	39s
testsuite / testsuite-linux (8.4, mysql, highest, false)	35s
testsuite / testsuite-linux (8.2, pgsql, highest, false)	32s
testsuite / testsuite-linux (8.3, sqlite, highest, false)	37s
testsuite / testsuite-linux (8.2, mysql, highest, false)	40s
testsuite / testsuite-linux (8.5, sqlite, highest, false)	34s
	4m 15s

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