feat(CLI):required arg parsing + first doit() call

We are parsing required scalar values and handle parse-errors correctly,
to the point were we make a simple, non-upload doit() call.

It shows that we seem to build invalid calls, for now,but that's nothing
we can't fix once the time is ripe.

Next goals will be related to finalizing the argument parsing code.

Fixes #60

src/rust/cli/cmn.rs

@@ -95,12 +95,14 @@ impl fmt::Display for ConfigurationError {
 #[derive(Debug)]
 pub enum CLIError {
     Configuration(ConfigurationError),
+    ParseError(String),
 }
 
 impl fmt::Display for CLIError {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         match *self {
-            CLIError::Configuration(ref err) => writeln!(f, "Configuration -> {}", err)
+            CLIError::Configuration(ref err) => writeln!(f, "Configuration -> {}", err),
+            CLIError::ParseError(ref desc) => desc.fmt(f),
         }
     }
 }