Can't build OabUtils successfully

[machiav3lli]

Since Rust 1.42 is std::error:Error::description fully deprecated and therefore the OabUtils can't be compiled. A clean up of main.rs and test_main.rs should do it. (Unfortunatly am not used to rust to help).

[machiav3lli]

the commit is a little bit dirty, nevertheless it fixes the problem:
NeoApplications@04e2beb