feat(builder): set log level programmatically

[davinkevin]

I'v created an enum with all the possible value and define a default value in the builder to the previous hard coded level (ERROR). The user can set verbosity with method setVerbosity(Verbosity v).
This will help us to develop the issue #21 because we need a certain level of information to display / send the progresion of a ffmpeg operation

[bramp]

The code looks good, but I avoided added this method, explicitly due to #21. Because I didn't know how to handle the case that a user setVerbosity(QUIET), and we are still expected to parse the output.

Perhaps discussion is needed on the parsing, but we could provide two interfaces. 1) Run with us parsing the output, or 2) Run with the user receiving the output and they can set verbosity?

I think until we have good answers it might be best to make this new method private, and document that we will open it in future when #21 is resolved.

[davinkevin]

We really need to synchronize ourself on the way we want to implement the #21 😄

I was thinking, for the first version of #21, the -v LOGLEVEL should be defined by the user, but, if he wants to be notified back by ffmpeg-cli-wrapper, the system will override the minimum LOGLEVEL to INFO.

[bramp]

Yes, we should sync :) Lets move discussion to #21, and start proposing how it will work, and what its goals are.