Implement EXPAND function

[Jython1415]

Overview

Implement the EXPAND function for the named-functions library.

Description

Expands or pads an array to specified row and column dimensions.

Value Proposition

• Fills arrays with specified values (default or custom pad value)
• Useful for normalizing array sizes before operations that require uniform dimensions
• Essential for matrix operations and array alignment
• Complements array manipulation toolkit

Priority

HIGH

Category

Array Manipulation

Implementation Notes

• Parameters: array, target_rows, target_columns, [pad_value]
• Default pad value should be configurable (typically empty string or NA)
• Should handle cases where target size is smaller than current array
• Consider behavior: error, truncate, or keep original size?
• Useful in combination with other array functions

Related

Part of Excel function implementation initiative (#51)

[Jython1415]

Implemented in #124