This change enable prefix search on Btrees

The following commits from your working branch will be included:

commit 0a1299c3d72b56a0045385cb9476ab99b1fbd7f6
Author: Abdullah Alamoudi <bamousaa@Abdullahs-MacBook-Pro.local>
Date:   Thu Oct 23 13:49:34 2014 +0300

    Enabled prefix search

Change-Id: Iebefb7c40d6eb7b55d023caaa148cc8512bd6e9e
Reviewed-on: http://fulliautomatix.ics.uci.edu:8443/126
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Taewoo Kim <wangsaeu@gmail.com>
diff --git a/asterix-app/src/test/resources/optimizerts/results/btree-index/btree-secondary-33.plan b/asterix-app/src/test/resources/optimizerts/results/btree-index/btree-secondary-33.plan
index 06194e4..d7667d6 100644
--- a/asterix-app/src/test/resources/optimizerts/results/btree-index/btree-secondary-33.plan
+++ b/asterix-app/src/test/resources/optimizerts/results/btree-index/btree-secondary-33.plan
@@ -3,6 +3,13 @@
     -- STREAM_SELECT  |PARTITIONED|
       -- STREAM_PROJECT  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- DATASOURCE_SCAN  |PARTITIONED|
+          -- BTREE_SEARCH  |PARTITIONED|
             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+              -- STABLE_SORT [$$9(ASC)]  |PARTITIONED|
+                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                  -- STREAM_PROJECT  |PARTITIONED|
+                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                      -- BTREE_SEARCH  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- ASSIGN  |PARTITIONED|
+                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|