filer store adds kv support

can compile now, need to implement those unimplemented

weed/filer/leveldb/leveldb_store_kv.go

@@ -0,0 +1,39 @@
+package leveldb
+
+import (
+	"context"
+	"fmt"
+)
+
+func (store *LevelDBStore) KvPut(ctx context.Context, key []byte, value []byte) (err error) {
+
+	err = store.db.Put(key, value, nil)
+
+	if err != nil {
+		return fmt.Errorf("kv put: %v", err)
+	}
+
+	return nil
+}
+
+func (store *LevelDBStore) KvGet(ctx context.Context, key []byte) (value []byte, err error) {
+
+	value, err = store.db.Get(key, nil)
+
+	if err != nil {
+		return nil, fmt.Errorf("kv get: %v", err)
+	}
+
+	return
+}
+
+func (store *LevelDBStore) KvDelete(ctx context.Context, key []byte) (err error) {
+
+	err = store.db.Delete(key, nil)
+
+	if err != nil {
+		return fmt.Errorf("kv delete: %v", err)
+	}
+
+	return nil
+}