Add null annotations to ConfigDescriptionRegistry and ConfigUtil (#1641)

Also added "org.eclipse.jdt.annotation" to the test BOM so we can use "org.eclipse.jdt.annotation.Checks" in itests.
That class has many useful methods that help with writing more readable test code when using the Eclipse JDT null analysis annotations.

After running the resolver on the itests  a lot of bundles were removed from the itest.bndrun files.

Signed-off-by: Wouter Born <github@maindrain.net>

bom/test/pom.xml

@@ -16,6 +16,11 @@
   <name>openHAB Core :: BOM :: Test</name>
 
   <dependencies>
+    <dependency>
+      <groupId>org.eclipse.jdt</groupId>
+      <artifactId>org.eclipse.jdt.annotation</artifactId>
+      <version>2.2.100</version>
+    </dependency>
     <dependency>
       <groupId>org.hamcrest</groupId>
       <artifactId>hamcrest-library</artifactId>