First release of Open AEA

AEA:

• Forks 1.1.0 of legacy AEA with the aim of maintaining backwards compatibility where possible
• Removes GOP decision maker handler to reduce dependencies
• Removes hard-coded registry API URL
• Changes default ledger to ethereum
• Removes dependency on fetchai packages
• Removes interact command

Plugins:

• Forks plugins, unfortunately cannot maintain plugin support for legacy aea plugins due to their dependency on legacy aea
• Fixes typing issues

Packages:

• Removes most fetchai packages apart from those currently used in tests
• Adds open_aea/signing:1.0.0 protocol

Docs:

• Removes most demos

Chores:

• Makes all necessary changes to move to open-aea