isce_utils: add unwrap_icu()

[yunjunz]

Description of proposed changes

• utils/isce_utils: add unwrap_icu() for pythonic re-use

• view: ignore whitespaces in output figure file name

Reminders

• Pass Pre-commit check (green)
• Pass Codacy code review (green)
• Pass Circle CI test (green)
• Make sure that your code follows our style. Use the other functions/files as a basis.
• If modifying functionality, describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.