Add clean logs support + dependent MR

Description

Add some mechanisms to add log support to Vivy.

• A LogSink is an object that will collect all the logs and emit them to a file, stderr, or in a Qt widget
• A Logger is the object used to create log message and submit them to the sink
• A LogMessage is a message, a line of log. You should not create it yourself, but use the macros or defined methods. They are submitted on destruction, so don't try things like auto msg = VIVY_LOG_WARN(appLog); msg << "toto"; unless you know what you are doing. If you don't pay attention, you might get log messages in a different order than what you originally wanted.

Example

Here is a small demo:

// Custom sink
VIVY_DCL_LOG_SINK(logSink) // Declare a Sink
std::shared_ptr<Logger> scriptLog = VIVY_GET_LOGGER(mySink, SCRIPT); // Custom logger
VIVY_LOG_WARN(scriptLog) << "This is" << ' ' << "very usefull!"; // Use the custom logger

// With the vivyApp's sink
class Object {
    // Add a logger to the sink and add log methods to the object
    VIVY_APP_LOGGABLE_OBJECT(Object, logger)

public:
    // ...
};

TODO List

• Create and use the API
• The simple stderr dispatcher
• The VivyConsoleDispatcher -> a dock widget with the MainWindow, like the console with VSCode or Eclipse
• Create the LogDispatcherThread -> flush at regular intervals the LogSink

Also merge dependent MR with this one to uniformize the logging process

src/Lib/Document/CRTPSubDocument/VideoSubDocument.cc

@@ -7,11 +7,7 @@ using namespace Vivy;
 void
 VideoSubDocument::initFromPath(const QString &path)
 {
-    if (contextPtr)
-        qDebug() << "Replacing the video contetx by a new one for file" << path;
     contextPtr.reset(new VideoContext(path)); // May throw
-
-    qDebug() << "Video OK for" << path;
 }
 
 QString