Migrate Java code to separate QL repo.

java/ql/src/DeadCode/UselessParameter.qhelp

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+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+<overview>
+<p>
+Parameters that are never read in the body of the method, and are not required due to overriding,
+are useless and can be removed. Useless parameters unnecessarily complicate the interface for that
+method, and cause a maintenance and development burden.
+</p>
+<p>
+Methods with useless parameters indicate that either the method can be simplified by removing the
+parameter, or that the method is not using a value it should be using. Parameters of methods that
+override other methods will not be marked as useless, because they are required. Similarly,
+parameters of methods that are overridden by other methods are not marked as useless if they are
+used by one of the overriding methods.
+</p>
+</overview>
+<recommendation>
+<p>
+The method should be inspected to determine whether the parameter should be used within the body.
+If the method is overridden, also consider whether any override methods should be using the
+parameter. If the parameter is not required, it should be removed.
+</p>
+</recommendation>
+<example>
+<p>
+In the following example, we have a method for determining whether a <code>String</code> path
+is an absolute path:
+</p>
+<sample src="UselessParameter.java" />
+<p>
+The method uses the parameter <code>path</code> to determine the return value. However, the
+parameter <code>name</code> is not used within the body of the method. The parameter will be marked
+as useless, and can be removed from the program.
+</p>
+</example>
+<include src="DeadCodeReferences.qhelp" />
+</qhelp>