Implement tracker for unused versions management

[Tremeschin]

Again, I'm doing this in Python (1) (2), but it will be much better to have the feature for everyone on pyaket! Will probably be a challenging one depending on the level of management done.

[Tremeschin]

Just a thought, but the way it could work is:

1. File {name}.uuid stores the hash of successful installations for $name project
2. Common file last-use tells if any project is already installed and idle since when

On hash mismatches or non-existing file (1), if (2) exists then the current binary should install in a rolling-release mode to keep all current files (venv --allow-existing), which properly solves sharing a venv in 2+ projects.

Problem now becomes racing conditions, when to update the last tracker file (save disk), to use a text content or file attributes, a library for time conversion into human text, a prompter, to save unix time or natural time?