[3.x] Adding a custom PIN code list (with optional default monitor sharing)

[rozsazoltan]

There should be a list where we can add our PIN codes, which we can share instantly with a single click. If there's a monitor associated with the PIN, it should be shared immediately (I believe handling specific windows would be too much work and error-prone). If no monitor is set, then - as it works currently - the user should manually select what content to share upon activation.

The new feature is having multiple fixed PIN codes that can be set as bookmarks in the browser on specific devices (TV, tablet, phone, etc.). This way, we know exactly which PIN corresponds to which sharing session on which device. For example, if I have two tablets and I always want to share the same two contents to them, I don't want to manually enter PIN codes each time. Instead, the first device would use a bookmark with PIN 00001 to instantly open the first shared session, and the second device would use a bookmark with PIN 00002 to open the second one.

It's a security risk, but there should be an option to allow force connection, meaning the server would not require any confirmation when a new device connects to a shared session. Of course, this should only be used at your own risk and in private environments. Otherwise, using this option is not recommended.