Gretel-synthetics

RC1. Adds "read only" most for Batches and default generation via CPUs with maximum parallelization.

🐛 Corrects calculation of `batch_size` when using the `DataFrameBatch` interface

🐛 When generating new lines via Batch mode, passed `max_invalid` param is now used vs the module default

🐞 Fix when synthetic Batches are converted back to a DataFrame with a custom field delimiter

Major changes to Gretel Synthetics including native support for DataFrames and batched column training!

⚙️ Introduce a ``batch`` module that allows a DataFrame to be ingested and split into batches of smaller DataFrames where each batch has a subset of the columns of the source DataFrame. This allows training of datasets with several columns while still allowing the preservation of correlations and statistical data. See our [Medium Blog](https://medium.com/gretel-ai) for details and our example ``dataframe_batch`` Notebook located in the ``examples`` directory.

📖 Massive updates to docstrings for the ``config`` module. Details for each config parameter.

🤖 Update to generation functionality. If a validator is provided, the ``gen_lines`` config option will be used only to count _valid_ lines that are generated. In order to stop run away generation, a ``max_invalid`` parameter exists that specifies the maximum number of invalid lines that can be generated. If this number of invalid lines is exceeded, a ``RunTimeError`` will be thrown and generation will be halted.