HUDI-123 Rename code packages/constants to org.apache.hudi (#830)

- Rename com.uber.hoodie to org.apache.hudi
- Flag to pass com.uber.hoodie Input formats for hoodie-sync
- Works with HUDI demo. 
- Also tested for backwards compatibility with datasets built by com.uber.hoodie packages
- Migration guide : https://cwiki.apache.org/confluence/display/HUDI/Migration+Guide+From+com.uber.hoodie+to+org.apache.hudi

hudi-common/src/main/avro/HoodieCleanMetadata.avsc

@@ -0,0 +1,24 @@
+{"namespace": "org.apache.hudi.avro.model",
+ "type": "record",
+ "name": "HoodieCleanMetadata",
+ "fields": [
+     {"name": "startCleanTime", "type": "string"},
+     {"name": "timeTakenInMillis", "type": "long"},
+     {"name": "totalFilesDeleted", "type": "int"},
+     {"name": "earliestCommitToRetain", "type": "string"},
+     {"name": "partitionMetadata", "type": {
+     "type" : "map", "values" : {
+        "type": "record",
+        "name": "HoodieCleanPartitionMetadata",
+        "fields": [
+            {"name": "partitionPath", "type": "string"},
+            {"name": "policy", "type": "string"},
+            {"name": "deletePathPatterns", "type": {"type": "array", "items": "string"}},
+            {"name": "successDeleteFiles", "type": {"type": "array", "items": "string"}},
+            {"name": "failedDeleteFiles", "type": {"type": "array", "items": "string"}}
+        ]
+     }
+     }
+     }
+ ]
+}