Fix issue#52 bug on parse defaults: defaults list are wrongly parsed,
add a *sanitize* before use defaults.

Concurrently add:

+ fix issue#57 on "cosmetic" help messages for hidden CLA;
+ make the call to `cli%parse` optional: when call `cli%get` for the
first time the CLI parsed status is checked an, if necessary,
`cli%parse` is automatically called;

Minor API changes: `cli%get` and `cli%get_varying` now accept also
string `args` for passing arguments by string to `cli%parse`.