Allow to use external libav in Windows builds

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
Do not pretend that EventData is a class
Force using QueuedConnections in RemotePortChecker

Application crashes on Windows when this is not set
Added more rules to gitignore files

Ignore build files on Windows
Added more files to OTHER_FILES section in .pro file
Added detailed instructions for building on Windows