Make awscli an optional dependency

[pculbertson-bdai]

As discussed in #3269, removes awscli from the main project dependencies in favor of a manual install by Eyeful Tower users.

Main changes:

• Removes awscli from pyproject.toml.
• Adds error handling on eyefultower.py prompting users to install awscli on ImportError.
• Adds error handling to download_data.py for case when awscli is not installed.
• Adds lines to documentation instructing Eyeful Tower users to manually install awscli.

[jb-ye]

Thx