cp file can work

1. consolidate to filer_pb.FileChunk
2. dir add file, mkdir
3. file flush, write

updates having issue

weed/filer2/embedded/embedded_store.go

@@ -3,6 +3,7 @@ package embedded
 import (
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/chrislusf/seaweedfs/weed/filer2"
+	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
 )
 
 type EmbeddedStore struct {
@@ -25,7 +26,7 @@ func (filer *EmbeddedStore) AddDirectoryLink(directory *filer2.Entry, delta int3
 	return nil
 }
 
-func (filer *EmbeddedStore) AppendFileChunk(fullpath filer2.FullPath, fileChunk filer2.FileChunk) (err error) {
+func (filer *EmbeddedStore) AppendFileChunk(fullpath filer2.FullPath, fileChunks []*filer_pb.FileChunk) (err error) {
 	return nil
 }