Update Documentation for v3

[Zalgo2462]

This PR is a first pass at addressing #441.

This PR brings the main README.md up to date for v3, mainly focusing on the changes to the import process.

The README.md has been edited to reflect the absence of the analyze step and the addition of rolling datasets.

In addition:

• references to Bro have been changed to Bro/Zeek in the main README
• IntenalSubnets typo has been fixed in the main README
• the "Examining Data" section has been updated to reflect the currently available show-x commands in the main README
• references to very old RITA configuration setups have been updated in the docs/ folder
• a small blurb has been added to Upgrading.md regarding the v3 transition. We may want to rewrite Upgrading.md in its entirety.

[ethack]

@Zalgo2462 Thanks so much for doing this!