Gracefully handle missing rules due to wrong PMD version

When using m2e + m2e-code-quality + pmd-eclipse-plugin, configuration of the project might fail, if the PMD versions don't match. E.g. the PMD version in the project might be newer than the one used by eclipse.

Example stack trace:

Sep. 27, 2018 2:01:59 NACHM. net.sourceforge.pmd.rules.RuleFactory buildRule
SCHWERWIEGEND: Error instantiating a rule
java.lang.ClassNotFoundException: net.sourceforge.pmd.lang.java.rule.basic.OverrideBothEqualsAndHashcodeRule cannot be found by net.sourceforge.pmd.eclipse.plugin_4.0.17.v20180801-1551
	at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:508)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:419)
	at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:411)
	at org.eclipse.osgi.internal.loader.ModuleClassLoader.loadClass(ModuleClassLoader.java:150)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)
	at net.sourceforge.pmd.rules.RuleBuilder.build(RuleBuilder.java:179)
	at net.sourceforge.pmd.rules.RuleFactory.buildRule(RuleFactory.java:189)
	at net.sourceforge.pmd.RuleSetFactory.parseSingleRuleNode(RuleSetFactory.java:562)
	at net.sourceforge.pmd.RuleSetFactory.parseRuleNode(RuleSetFactory.java:461)
	at net.sourceforge.pmd.RuleSetFactory.parseRuleSetNode(RuleSetFactory.java:367)
	at net.sourceforge.pmd.RuleSetFactory.createRuleSet(RuleSetFactory.java:214)
	at net.sourceforge.pmd.RuleSetFactory.createRuleSet(RuleSetFactory.java:209)
	at net.sourceforge.pmd.RuleSetFactory.createRuleSets(RuleSetFactory.java:170)
	at net.sourceforge.pmd.RuleSetFactory.createRuleSets(RuleSetFactory.java:154)
	at net.sourceforge.pmd.eclipse.runtime.properties.impl.ProjectPropertiesManagerImpl.loadRuleSetFromProject(ProjectPropertiesManagerImpl.java:175)
	at net.sourceforge.pmd.eclipse.runtime.properties.impl.ProjectPropertiesManagerImpl.fillProjectProperties(ProjectPropertiesManagerImpl.java:246)
	at net.sourceforge.pmd.eclipse.runtime.properties.impl.ProjectPropertiesManagerImpl.loadProjectProperties(ProjectPropertiesManagerImpl.java:116)
	at net.sourceforge.pmd.eclipse.plugin.PMDPlugin.loadProjectProperties(PMDPlugin.java:510)
	at net.sourceforge.pmd.eclipse.runtime.cmd.ReviewCodeCmd.getProjectProperties(ReviewCodeCmd.java:442)
	at net.sourceforge.pmd.eclipse.runtime.cmd.ReviewCodeCmd.processResourceDelta(ReviewCodeCmd.java:616)
	at net.sourceforge.pmd.eclipse.runtime.cmd.ReviewCodeCmd.execute(ReviewCodeCmd.java:219)
	at net.sourceforge.pmd.eclipse.runtime.cmd.JobCommandProcessor$1.run(JobCommandProcessor.java:93)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:60)

Other example:

An internal error occurred during: "Updating Maven Project".
Unable to find referenced rule IdenticalCatchBranches; perhaps the rule name is mispelled?

Reproduce the failure with m2e, m2e-code-quality, and mismatched PMD versions, then trace the stack from RuleFactory and RuleBuilder through RuleSetFactory to ProjectPropertiesManagerImpl. Determine the expected behavior for missing rules and verify that project configuration reports or handles the mismatch without the shown internal error.