Python-weka-wrapper3

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- added `logging_level` parameter to the `start` method of the `weka.core.jvm` module, enabling the user
to turn off debugging output in an easy way (https://github.com/fracpete/python-weka-wrapper3/issues/40)
- added method `cv_splits` to class `Instances` from module `weka.core.dataset` to return a list of
train/test tuples as used by cross-validation
- the `Tester` class (module: `weka.experiments`) now has an option to swap columns/rows for comparing
datasets rather than classifiers
- the `SimpleExperiment` class and derived classes (module: `weka.experiments`) now have the additional
parameters in the constructor: class_for_ir_statistics, attribute_id, pred_target_column
- the method `is_installed` (module: `weka.core.packages`) now can check whether a specific version is installed
- added `pww-packages` entry point to allow managing of Weka packges from the command-line
(actions: list/info/install/uninstall/suggest/is-installed)

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- method `JavaObject.new_instance` in module `weka.core.classes` now automatically
installs packages based on suggestions if the JVM was started with the `auto_install`
flag enabled.
- method `test_model_once` of class `Evaluation` (module: `weka.classifiers`) now has the
additional parameter `store`, which allows the recording of the predictions (necessary
for statistics like AUC)

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- methods `create_instances_from_lists` and `create_instances_from_matrices`
(module `weka.core.dataset`) now allow the specification of column names,
for input and output variables.

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- Added property for attribute indices to `DistanceFunction` class (module `weka.core.distances`)
(thanks to Martin Trat, https://github.com/fracpete/python-weka-wrapper3/pull/39)
- improved instantiation of classes, avoiding misleading output of exceptions
- `JavaArray` class (module: `weka.core.classes`) now has `__str__` and `__repr__` methods that output
classname and size

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- upgraded bundled Weka to 3.9.6

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- switched to `python-javabridge`, the new name (fork?) of the `javabridge` library
- `Package.__str__` (`weka.core.packages` module) method now returns a string rather than printing the name/version
- added `to_numpy(...)` methods to `Instance` and `Instances` classes (module `weka.core.dataset`)
to make it easy to obtain a numpy array from the Weka dataset