Added the ability to get VLC log messages from the application

[jeremyVignelles]

Added the ability to hook a .net event handler to libvlc.

It has the limitation of libvlc, i.e. it does not offer the ability to get logs from the very beginning of the libvlc instanciation.

What has changed for the library users:

• New Log event has been created
• If Log is not used, the behavior is left unchanged
• If the Log event is listened, before or after EndInit (both cases are handled), the libvlc logger (that writes the vlc-log.txt file) is stopped and all logs are transferred to the application. If you remove the Log event handler, the previous logger is not restored

Things to be discussed before merging:

• Do we need to get more info than just the message string? i.e. do we need to use libvlc_log_get_context to get the module, file and line?
• Look at why the libvlc version does not appear in the log (it should)
• Resolve why AppVeyor has failed to build

[ZeBobo5]

Please check errors to be able to merge.

[jeremyVignelles]

Done !

Please tell me if you need anything else related to logging.

[ZeBobo5]

Perfect. Thanks for contribution

[jeremyVignelles]

You're welcome 😄

I'd like to get more involved in this project, because I need it at work. I try to answer the questions in the "issues" section but there are too many of them, some of which are not relevant and others have been solved but not closed.
Could you do this or do you want to add me as a contributor so that I can close them?

[honfika]

@ZeBobo5 I really appreciate that you created this project (we are also using it in our project), but please add somebody to the contributors if you don't have time to check and merge the new pull requests, answer to the issues.
I also want to improve you project but it is demotivating if somebody has to wait weeks before his change is merged. Thank you.

[ZeBobo5]

Sorry for long time response, I was not available. If you want to contribute, I can add you :)

[honfika]

Thank you, please add me too if it is possible. I'd like to contribute in this project., too

[jeremyVignelles]

@honfika : I don't have the rights to do so, but I'd be happy to work with you :) Every contribution is welcome. I'll create a gitter for the project so that we can communicate with each other

[ZeBobo5]

@honfika : I just send you invitation too. Thanks for contributions