Receive cargo home as a parameter via local.properties

[andrefigas]

• Added support for using a custom Rust installation directory, as long as it is defined in local.properties using the cargo.dir property.
• Moved Rust version validation from the configuration phase to the Rust code compilation phase.

This will close issue #32.

[DocteurPing]

LGTM! i haven't try to run the code to see if everything if working as expected.
Update: This has been tested. it works fine.