Fix to DELF package (#8679)

* First version of working script to download the GLDv2 dataset

* First version of the DEFL package installation script

* First working version of the DELF package installation script

* Fixed feedback from PR review

* Push to Github of changes to the TFRecord data generation script for DELF.

* Merged commit includes the following changes:
315363544  by Andre Araujo:

    Added the generation of TRAIN and VALIDATE splits from the train dataset.

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314676530  by Andre Araujo:

    Updated script to download GLDv2 images for DELF training.

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314101235  by Andre Araujo:

    Added newly created module 'utils' to the copybara script.

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313677085  by Andre Araujo:

    Code migration from TF1 to TF2 for:
    - logging (replaced usage of tf.compat.v1.logging.info)
    - testing directories (replaced usage of tf.compat.v1.test.get_temp_dir())
    - feature/object extraction scripts (replaced usage of tf.compat.v1.train.string_input_producer and ...

research/delf/delf/__init__.py

@@ -25,7 +25,6 @@ from delf.protos import delf_config_pb2
 from delf.protos import feature_pb2
 from delf.python import box_io
 from delf.python import datum_io
-from delf.python import delf_v1
 from delf.python import feature_aggregation_extractor
 from delf.python import feature_aggregation_similarity
 from delf.python import feature_extractor