ICU-20568 Use `Impl` libraries, add precision UnitsRouter#route output

ICU-20568 Use `Impl` libraries, add precision UnitsRouter#route output

Add precision to the output of UnitsRouter#route
PR: https://github.com/icu-units/icu/pull/10
Commit: 030bda3ec86a02b190a83798a7c9be530a335067

Use `Impl` libraries for all internal libraries
PR: https://github.com/icu-units/icu/pull/15
Commit: cc786cfb3bee3c72e78a928da8b9a6fd58f31b04

Sort the units in ComplexUnitConverter
PR: https://github.com/icu-units/icu/pull/6
Commit: f65b181c4447bb4eb9eef5dc20ea1b296d053ffa