Ccm.java:88-94: Implement NCC calculation with `XmlGraph`...

[0pdd]

The puzzle 449-dd12396b from #449 has to be resolved:

jpeek/src/main/java/org/jpeek/calculus/java/Ccm.java

Lines 88 to 94 in 18efdff

	* @todo #449:30min Implement NCC calculation with `XmlGraph` and use this
	* class to fix CCM metric (see issue #449). To do this, this class, once
	* it works correctly, should be integrated with XSL based calculuses in
	* `XslReport` (see `todo #449` in Calculus). Write a test to make sure
	* the metric is calculated correctly. Also, decide whether the
	* whole CCM metric should be implemented in Java, or only the NCC part.
	* Update this `todo` accordingly.

The puzzle was created by yegor256 on 05-Feb-21.

Estimate: 30 minutes, role: DEV.

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