Add command-line support for No-reference metrics

[naderelhadedy]

Command line support is currently limited to full-reference metrics only.

sewar mse 'path/to/image1' 'path/to/image2'

So, we need to add support for no-reference metrics too.

[naderelhadedy]

@andrewekhalel I'll work on this.

[andrewekhalel]

Sounds good @naderelhadedy. Thanks!