Virtualfish

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* Projects + Auto-Activation: Auto-deactivate when leaving project directory
* global_requirements: Don't manually build wheels
* Fix erroneous minimum Fish version

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Improve Fish version check reliability. Upon failure, warn instead of exiting.

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* Ensure minimum required Fish shell version is present when installing
* Prevent error on older Fish shell versions

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When uninstalling, use same Python interpreter used to install VirtualFish

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Running `vf ls` no longer modifies directory history

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* `rm`: Allow multiple virtual environment deletion with single invocation
* `auto_activation`: After `vf connect`, de-activate when leaving project directory
* Remove unnecessary `xdg` Python dependency