Update LMDBDataset to support batch at the creation

This PR updates LMDBDataset to support batch at the creation,
it also switch to the new pattern to reduce unnecessary code
duplication.

Signed-off-by: Yong Tang <[email protected]>

Author: yongtang

tensorflow_io/core/BUILD

@@ -35,6 +35,7 @@ cc_library(
         ".",
     ],
     deps = [
+        "@libarchive",
         "@local_config_tf//:libtensorflow_framework",
         "@local_config_tf//:tf_header_lib",
     ],

tensorflow_io/lmdb/BUILD

@@ -5,8 +5,8 @@ package(default_visibility = ["//visibility:public"])
 cc_binary(
     name = "python/ops/_lmdb_ops.so",
     srcs = [
-        "kernels/lmdb_dataset_ops.cc",
-        "ops/dataset_ops.cc",
+        "kernels/lmdb_input.cc",
+        "ops/lmdb_ops.cc",
     ],
     copts = [
         "-pthread",
@@ -15,6 +15,7 @@ cc_binary(
     ],
     linkshared = 1,
     deps = [
+        "//tensorflow_io/core:dataset_ops",
         "@lmdb",
         "@local_config_tf//:libtensorflow_framework",
         "@local_config_tf//:tf_header_lib",

tensorflow_io/lmdb/__init__.py

@@ -21,7 +21,7 @@
 from __future__ import division
 from __future__ import print_function
 
-from tensorflow_io.lmdb.python.ops.lmdb_dataset_ops import LMDBDataset
+from tensorflow_io.lmdb.python.ops.lmdb_ops import LMDBDataset
 
 from tensorflow.python.util.all_util import remove_undocumented