Add isLimelightConnected to pose estimation

[Ishan1522]

You can view it here. I added this a while ago for sim testing (a basic check if I was getting info from the simulated camera, or if i fucked up).
Basically we can incorporate this into our enabledPoseUpdate() as a check to see if a limelight is connected, and it will not do pose estimation for that limelight if the network table doesn't exist anymore.

This task might seem slightly complex at first, but is definitely accomplish-able by a minion.