OBC Epoch Relative Commands

[richarthurs]

Right now, "scheduling" a command just means that we send it out at some point in the future, to be run immediately on the OBC.

We also need the ability to use the OBC's scheduling system. This means we can uplink commands that include information to tell the OBC when to run them, as we would in space.

There is a checkbox on the command creator tab that sets the command to be relative time. Relative time means the time used is relative to when the "uplink" button is pressed (the current behaviour). The other option is an absolute command, where we will use the OBC clock to internally schedule the command.

1. SCHEDTab.py line 38, set the rel argument of the Command constructor to be the value of the check box
2. Modify the existing command uplink logic to handle commands with rel = true as they are handled right now.
3. When creating a command with rel = False, the epoch given in the command is the absolute epoch on the satellite when we want to run the command. So, upon clicking uplink, for absolute commands, we must:
   -- get the current epoch from the satellite
   -- subtract that from the scheduled epoch in the command. Discard the command if the result is negative
   -- uplink the command to the satellite at a time of [previous result] seconds from uplink press
4. Get that working. You can use self.test (the satTest class) to contain the current epoch from the satellite (it should be represented the actual seconds from the sat, and the computer time)
5. Once that works, absolute commands can be transformed into satellite sched commands where the result of the subtraction above becomes the command's secondsFromNow field. Upon creating that command, it can be instantly uplinked to the satellite for the satellite to handle.