Support an easy migration path from volare

[mithro]

Description

It would be great if ciel detected you had volare currently installed and offered to migrate you to ciel.

This would be particularly great for the PDK data, as it can get large rather quickly.

Proposal

I ended up doing the following;

1. Renaming the ~/.volare directory to ~/.ciel
2. Renaming the ~/.ciel/volare to ~/.ciel/ciel
3. Creating a symlink from ~/.ciel to ~/.volare
4. Creating a symlink in ~/.ciel from ciel to volare

This seems to allow both volare and ciel to see the PDKs I have previously installed via volare.

I have no idea if doing this is super dangerous / stupid or similar.