environment updates/upgrades break on local registry

[RMichae1]

When updating/upgrading or reinstalling the local ~/.poli_objectives/ directory becomes stale.

This yields an execution error where poli looks for the incorrect executables, based on old paths.

This requires a manual purge of the registered objectives, whenever changing the environment.

This needs to be hands-off for the user and should only be required to be interacted with under special/power-user circumstances.

[RMichae1]

This is still an issue that breaks black-box executions on upgrades of the environments. Should be prioritized for a fix.