Pi classes to support P4Runtime action profiles

+ modified default.p4 with ECMP capabilities (via action profiles)
+ sketched translation logic of ONOS groups (in Bmv2GroupProgrammable)
+ replaced existing instances of default.json/p4info with symlinks to
	p4src build directory (to avoid inconsistencies)

Change-Id: If82f0b8ce296c9b616415d99864d216b77645a87
diff --git a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionGroupMemberId.java b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionGroupMemberId.java
new file mode 100644
index 0000000..8669388
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionGroupMemberId.java
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.net.pi.runtime;
+
+import com.google.common.annotations.Beta;
+import org.onlab.util.Identifier;
+
+/**
+ * Identifier of a member of an action group in a protocol-independent pipeline.
+ */
+@Beta
+public final class PiActionGroupMemberId extends Identifier<Integer> implements PiTableAction {
+
+    private PiActionGroupMemberId(int id) {
+        super(id);
+    }
+
+    /**
+     * Returns an action group identifier for the given integer value.
+     *
+     * @param id identifier
+     * @return action group
+     */
+    public static PiActionGroupMemberId of(int id) {
+        return new PiActionGroupMemberId(id);
+    }
+
+    /*
+    In P4Runtime, group members can be referenced directly as table actions.
+    In future we should consider having a more appropriate wrapper class for group member IDs, instead of implementing
+    the PiTableAction interface.
+     */
+    @Override
+    public Type type() {
+        return Type.GROUP_MEMBER_ID;
+    }
+}