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/HoodieCompactionMetadata.avsc

@@ -0,0 +1,42 @@
+{
+   "namespace":"org.apache.hudi.avro.model",
+   "type":"record",
+   "name":"HoodieCompactionMetadata",
+   "fields":[
+      {
+         "name":"partitionToCompactionWriteStats",
+         "type": ["null", {
+            "type":"map",
+            "values":{
+               "type":"array",
+               "items":{
+                  "name":"HoodieCompactionWriteStat",
+                  "type":"record",
+                  "fields":[
+                     {
+                        "name":"partitionPath",
+                        "type":["null","string"]
+                     },
+                     {
+                        "name":"totalLogRecords",
+                        "type":["null","long"]
+                     },
+                     {
+                        "name":"totalLogFiles",
+                        "type":["null","long"]
+                     },
+                     {
+                        "name":"totalUpdatedRecordsCompacted",
+                        "type":["null","long"]
+                     },
+                     {
+                        "name":"hoodieWriteStat",
+                        "type":["null","HoodieWriteStat"]
+                     }
+                  ]
+               }
+            }
+         }]
+      }
+   ]
+}