Python-ags4

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- Updated thresholds for table sizes to trigger warning when exporting to Excel
- Made the conversion to and from Excel more robust:
- Warnings and user input added when importing large files to Excel
- Stray data from Excel files filtered out when importing to .ags
- Added rich as a dependency
- Added CLI interface
- Updated excel_to_AGS4() to autoformat numeric columns based to match
the specification in the TYPE row. The data in the UNIT/TYPE rows will
be overridden if a dictionary file is provided as input.
- Updated convert_to_text() so that it can handle TYPEs with more than
one digit (e.g. '10DP', '12SCI') without crashing. [Asitha Senanayake]
- Moved import of pd.DataFrame to inside the AGS4_to_dataframe()
function so that it does get added to the AGS4 namespace.
- Made convert_to_text() function more robust with error catching for
non-numeric values.
- Added functionality to auto format columns of TYPE "nSF" with the
convert_to_text()
- AGS4_to_dict() now checks whether the number of columns in UNIT, TYPE,
and DATA rows match the number in the HEADING row

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- Added AGS4_to_excel() and excel_to_AGS4() functions to import/export
.ags files to/from .xlsx files

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- Updated dataframe_to_AGS4() so that it can be called without having
explicitly provide a dictionary of headings. It can now accept an empty
headings dictionary
- Added convert_to_text() function to convert DataFrames containing numeric
data back to formatted text fields that can be exported back to a .ags
file

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- Set default encoding to utf-8 when reading and writing files

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- Removed the set_index_to_heading option in AGS4_to_dataframe() to avoid
errors in AGS4 files re-exported using the dataframe_to_AGS4() function.
dataframe_to_AGS4() does not export the index of the dataframe when
exporting so having the headings column as the index will create an erroneous
AGS4 file.
- Update dataframe_to_AGS4() so that line terminations are \r\n as per AGS4
Rule 2a.

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- Update dataframe_to_AGS4() function to avoid unnecessary blank lines between
rows when used in Windows.