Support multiple versions of the same dependency

[mario-eth]

In order to respect the Cargo.toml format for now the dependency name is used as key in the config file.
In the future we must implement something like this:

libv1 = { version = "1", package = "lib" }
libv2 = { version = "2", package = "lib" }

Example
https://github.com/TheDan64/inkwell/blob/69c5a3fcc3e8b997c36e20021c52adcff664d746/Cargo.toml#L129-L150