Allow clarifying different versions of the same crate separately

**Is your feature request related to a problem? Please describe.**
When there are duplicate dependencies with different versions in the tree and `cargo-about` is not able to correctly determine the licensing situation it would be nice if we could clarify both versions of the crate separately in case they have slightly different licensing situations.

**Describe the solution you'd like**
Allow (optionally) to specify a version on the clarification.

Examples of how this could look like:
- ```toml
[crate.'0.1.0'.clarify]
license = "..."

[[crate.'0.1.0'.clarify.files]]
# ...
```
- ```toml
['crate-0.1.0'.clarify]
license = "..."

[['crate-0.1.0'.clarify.files]]
# ...
```

The issue names no files or tests. Start by locating the TOML configuration parsing and clarification matching entry points, then verify how duplicate crate versions are identified. Done means an optional version-qualified clarification can be configured and applied separately to each version.

Written by the indexing model from the issue text.