Properly detect if packages are a git installation over directory installation

Resolution speed improvement

Fix warning about  self update when using install-poetry.py

Relates-to: #2899

* handle poetry init non-interactive dependencies

1. in non-interactive mode, suppress "This command will guide you through..."
2. in interactive mode, respect command line --dependency if the user chooses NO for "Would you like to define your main dependencies interactively?"

Fix locked information for path, url and VCS dependencies

Fix documentation relative reference

Reorganize documentation

replace f-string in get-poetry by `.format()` for python2 compatibility

Relates-to: #4040

When installing poetry < 1.2.0a1 add a warning indicating the breakage
of `self update` command usage.

Relates-to: #4040

Relates-to: #4040

Release 1.2.0a1

Improve the `self update` command to account for the new installer

Resolves: #3964
Co-authored-by: Sébastien Eustace <sebastien.eustace@gmail.com>
Co-authored-by: Arun Babu Neelicattu <arun.neelicattu@gmail.com>

keyring appears to be increasing the major version for minor changes every few months: https://github.com/jaraco/keyring/compare/v22.4.0...v23.0.0

Perhaps it would be better to use a >= dependency here?

Some docs used "you" where they should use "your" for possessiveness.

env: default to enabling pip/wheels/setuptools

For project virtual environments, default to enabling pip, setuptools
and wheel packages to retain existing stable behaviour to prevent
unexpected breakages caused by development environments making
assumptions of base package availability in virtual environments.

Poetry itself does not require the use of these packages and will
execute correctly within environments that do not have these packages.

This change retains the ability to manage these packages as direct
project dependency as introduced in #2826. All poetry internal
execution of pip is retaining the use of the wheel embedded within
the virtualenv package used by poetry.

In cases where a one of these reserved packages are being managed as a
project dependency, the will be treated as any other project
dependency. Executing `poetry install --remove-untracked` will not
remove any of these reserved packages. However, `poetry add pip` and
`poetry remove pip` will trigger the update and removal of `pip`
respectively.

Relates-to: #2826
Relates-to: #3916

Previously, pytest execution was influenced by poetry user
configuration. This change ensures that a new config.toml is used each
test case.

Replace updates of os.environ with explicit passing of `env` to
subprocess calls in `Env.execute()`.

Relates-to: #3199