fix user guide describing wrong default behavior of @AnalyzeClasses (…

…#1406)

The user guide claims that without specifying anything `@AnalyzeClasses`
will import the whole classpath.
This is not true anymore since release 1.0, because we changed the
default behavior to import the package of the annotated test class.
The user guide now reflects this correctly and also mentions the option
`wholeClasspath` to restore the old behavior.

Resolves: #1401

docs/userguide/009_JUnit_Support.adoc

@@ -73,7 +73,7 @@ For further information see <<Controlling the Cache>>.
 ==== Controlling the Import
 
 Which classes will be imported can be controlled in a declarative way through `@AnalyzeClasses`.
-If no packages or locations are provided, the whole classpath will be imported.
+If no packages or locations are provided, the package of the annotated test class will be imported.
 You can specify packages to import as strings:
 
 [source,java,options="nowrap"]
@@ -116,6 +116,13 @@ production code, and only consider code that is directly supplied and does not c
 As explained in <<The Core API>>, you can write your own custom implementation of `ImportOption`
 and then supply the type to `@AnalyzeClasses`.
 
+To import the whole classpath, instead of just the package of the test class, use the option
+
+[source,java,options="nowrap"]
+----
+@AnalyzeClasses(wholeClasspath = true)
+----
+
 ==== Controlling the Cache
 
 By default, all classes will be cached by location. This means that between different