[ASTERIXDB-2244][RT] Implement micro union-all operator

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- implement support for binary micro operators in subplans
- implement micro union-all operator
- fix free variables visitor

Change-Id: I11be926f175889978c144dd4483ec565d3d86e2d
Reviewed-on: https://asterix-gerrit.ics.uci.edu/2277
Reviewed-by: Till Westmann <tillw@apache.org>
Contrib: Till Westmann <tillw@apache.org>
Integration-Tests: Till Westmann <tillw@apache.org>
Tested-by: Till Westmann <tillw@apache.org>
diff --git a/hyracks-fullstack/algebricks/algebricks-runtime/pom.xml b/hyracks-fullstack/algebricks/algebricks-runtime/pom.xml
index bbea2ab..dafb6ab 100644
--- a/hyracks-fullstack/algebricks/algebricks-runtime/pom.xml
+++ b/hyracks-fullstack/algebricks/algebricks-runtime/pom.xml
@@ -73,6 +73,10 @@
       <version>${project.version}</version>
     </dependency>
     <dependency>
+      <groupId>org.apache.commons</groupId>
+      <artifactId>commons-lang3</artifactId>
+    </dependency>
+    <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
     </dependency>