[maven-release-plugin] prepare release pmd_releases/5.1.0
[maven-release-plugin] prepare for next development iteration
pmd: update release process documentation

  pmd.website.baseurl is set correctly if the profile "pmd-release" is used
  during releasing
pmd: format source, no changes
pmd: fix #1171 Specifying minimum priority from command line gives NPE
pmd: fix #1175 false positive for StringBuilder.append called 2 consecutive times
pmd: verify #1173 Java 8 support: method references
pmd: fix #1170 false positive with switch in loop
pmd: fix #1173 Java 8 support: method references
pmd: fix #1176 ShortVariable false positive with for-each loops
pmd: fix #1178 LexicalError while parsing Java code aborts CPD run
pmd/cpd: add skipLexicalErrors and skipDuplicateFiles to CPD's ant task
pmd: fix #1177 Incorrect StringBuffer warning when that class is not used
pmd: fix #1180 False Positive for ConsecutiveAppendsShouldReuse on different variable names
pmd: fix #1168 Designer errors when trying to copy xml to clipboard
Document that PMD requires java 1.6
Fix unit test DesignerTest so that it runs in headless mode, too.
Fix comments between other comments being wrongly assigned:

	/** Comment 1 */
	public void method1() {}

	/** Comment 2 */

	/** Comment 3 */
	public void method2() {}

Would assign Comment 2 to method2, should assign Comment 3.

Also added support for enums in AbstractCommentRule.orderedCommentsAndDeclarations().
Add unit test for bug #1166 PLSQL XPath Rules Fail for XPath 1.0
PLSQL- Add minimal XPathHandler to PLSQLHandler in order to avoid NPE in XPath rules for XPath 1.0.