AEA-443 prepare develop for v0.2.3

[DavidMinarsch]

Proposed changes

This PR restructures the docs based on feedback and upgrades the version.

Fixes

Types of changes

What types of changes does your code introduce to agents-aea?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING doc
• I am making a pull request against the develop branch (left side). Also you should start your branch off our develop.
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have checked that code coverage does not decrease.
• I have checked that the documentation about the aea cli tool works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

[codecov-io]

Codecov Report

Merging #946 into develop will increase coverage by 0.06%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #946      +/-   ##
===========================================
+ Coverage    96.16%   96.23%   +0.06%     
===========================================
  Files          120      120              
  Lines         8911     8913       +2     
===========================================
+ Hits          8569     8577       +8     
+ Misses         342      336       -6

Flag	Coverage Δ
#unittests	96.23% <100%> (+0.06%)	⬆️

Impacted Files	Coverage Δ
aea/__version__.py	100% <100%> (ø)	⬆️
aea/crypto/ethereum.py	100% <0%> (ø)	⬆️
packages/fetchai/connections/local/connection.py	99.5% <0%> (ø)	⬆️
aea/protocols/generator.py	99.37% <0%> (+0.25%)	⬆️
aea/cli_gui/__init__.py	87.54% <0%> (+0.32%)	⬆️
aea/decision_maker/base.py	100% <0%> (+0.63%)	⬆️
aea/helpers/base.py	100% <0%> (+1.58%)	⬆️

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[DavidMinarsch]

Changing names to avoid clashes with pytest loading module.

[marcofavorito]

LGTM

[Totoual]

Do we need a specific version here?

[Totoual]

LGTM