Restructure exercise directory

Reference solution directory was renamed and move to the
always-excluded-from-delivery .meta folder.

CONTRIBUTING.md

 
 There are two objectives to the design of this build:
 
-1. when a problem is built from within the `exercism/java` repo (i.e. when you, the contributor, are developing the exercise), the tests run against the "example" code;
+1. when a problem is built from within the `exercism/java` repo (i.e. when you, the contributor, are developing the exercise), the tests run against the reference solution;
 2. when a problem is built outside the `exercism/java` repo (when a participant is solving the exercise), the tests run against the "main" code.
 
 This repo is a multi-project gradle build.
 
 This is the top-level module, contained in the `exercises` directory.  It is a container for the problem sub-modules.
 
-  * its `build.gradle` points the "main" sourceset to the example code.
+  * its `build.gradle` points the "main" sourceset to the reference solution.
   * its `settings.gradle` names each of the subprojects, one for each problem in the set.
 
 ### The Problem Submodules
 Each problem/submodule has three source sets:
 
 * `src/test/java/` — a test suite defining the edges of the problem
-* `src/example/java/` — an example solution that passes all the tests
+* `./meta/src/reference/java/` — a reference solution that passes all the tests
 * `src/main/java/` — starter source files, if required/desired *(this directory usually only has a `.keep` file in it)*.
 
 ----

bin/journey-test.sh

     echo "=================================================="
 
     ${exercism_cli} fetch ${TRACK} $exercise
-    cp -R -H ${track_root}/exercises/${exercise}/src/example/${TRACK}/* ${exercism_exercises_dir}/${TRACK}/${exercise}/src/main/${TRACK}/
+    cp -R -H ${track_root}/exercises/${exercise}/.meta/src/reference/${TRACK}/* ${exercism_exercises_dir}/${TRACK}/${exercise}/src/main/${TRACK}/
 
     pushd ${exercism_exercises_dir}/${TRACK}/${exercise}
     # Check that tests compile before we strip @Ignore annotations
   echo "=================================================="
 
   ${exercism_cli} fetch ${TRACK} $exercise_to_solve
-  cp -R -H ${track_root}/exercises/${exercise_to_solve}/src/example/${TRACK}/* ${exercism_exercises_dir}/${TRACK}/${exercise_to_solve}/src/main/${TRACK}/
+  cp -R -H ${track_root}/exercises/${exercise_to_solve}/.meta/src/reference/${TRACK}/* ${exercism_exercises_dir}/${TRACK}/${exercise_to_solve}/src/main/${TRACK}/
 
   pushd ${exercism_exercises_dir}/${TRACK}/${exercise_to_solve}
   # Check that tests compile before we strip @Ignore annotations

config.json

     "grains",
     "say"
   ],
-  "language": "Java"
+  "language": "Java",
+  "solution_pattern": "reference"
 }

exercises/build.gradle

 // This root Gradle project is used for:
 //
-// - Checking that every test suite compiles against its corresponding example implementation;
-// - Checking that every example implementation passes its corresponding test suite;
+// - Checking that every test suite compiles against its corresponding reference implementation;
+// - Checking that every reference implementation passes its corresponding test suite;
 // - Checking that every provided starter implementation compiles.
 //
 // This file is never delivered to Exercism users.
   afterEvaluate { project ->
 
     sourceSets {
-      // Set the directory containing the example implementation as the default source set. Default
+      // Set the directory containing the reference solution as the default source set. Default
       // compile tasks will now run against this source set.
       main {
-        java.srcDirs = ["src/example/java"]
+        java.srcDirs = [".meta/src/reference/java"]
       }
 
       // Define a custom source set named "starterSource" that points to the starter implementations