DevTools: [CodeMirror] Implement "select next occurrence" functionality

LayoutTests/inspector/editor/text-editor-ctrl-d-expected.txt

+This test verifies Ctrl-D functionality, which selects next occurrence of word.
+
+function wordData() {
+    return {
+        original: $(".entry.original > .input").text(),
+        translation: $(".entry.translation > .input").text(),
+        tags: $(".active-tags > .tagcloud > .tag").toArray().map(function(value) { return value.textContent; })
+    };
+}
+
+function submitWord(url) {
+    var stub = new App.Stub($(".content"));
+    $.post(url, wordData())
+    .done(function() {
+        var callback = $("meta[data-callback]").attr("data-callback");
+        if (callback) {
+            window.location = callback;
+        } else {
+            stub.success();
+            $(".entry.original > .input").text("").focus();
+            $(".entry.translation > .input").text("");
+        }
+    })
+    .fail(function(obj, err, errDescr) {
+        stub.failure("Error: " + errDescr);
+    })
+}
+
+Running: testNextFullWord
+'function': 3
+
+Running: testOccurrencesOnTheSameLine
+'original': 3
+
+Running: testTwoCloseWords
+'text': 4
+
+Running: testCursorInTheWordStart
+'function': 1
+
+Running: testCursorInTheWordEnd
+'function': 1
+
+Running: testNonWordSelection
+'$(': 7
+
+Running: testNonWordSelection2
+' > ': 6
+
+Running: testNonWordSelection3
+'window.location': 1
+'success': 1
+'text(': 1
+
+Running: testNonWordSelection4
+'text(': 4
+'dow.locati': 1
+'es': 1
+
+Running: testTriggerWordSearchInMixedCase
+'stub = new App.Stub': 1
+'callback': 5
+