filer store adds kv support

can compile now, need to implement those unimplemented

weed/filer/abstract_sql/abstract_sql_store_kv.go

@@ -0,0 +1,18 @@
+package abstract_sql
+
+import (
+	"context"
+	"github.com/chrislusf/seaweedfs/weed/filer"
+)
+
+func (store *AbstractSqlStore) KvPut(ctx context.Context, key []byte, value []byte) (err error) {
+	return filer.ErrKvNotImplemented
+}
+
+func (store *AbstractSqlStore) KvGet(ctx context.Context, key []byte) (value []byte, err error) {
+	return nil, filer.ErrKvNotImplemented
+}
+
+func (store *AbstractSqlStore) KvDelete(ctx context.Context, key []byte) (err error) {
+	return filer.ErrKvNotImplemented
+}