Start and stop headless GRIP using NetworkTables

[ThomasJClark]

This lets robot programs start and stop GRIP to save CPU without having
to wait for the process to start up again.

For example,

NetworkTable table = NetworkTable.getTable("GRIP");

table.putBoolean("run", false); // Stop GRIP without killing the process

doSomeStuffThatDoesntNeedVision();

table.putBoolean("run", true); // Start GRIP again

This should be useful for teams that want to do auto alignment in teleop, since they could start and stop vision processing whenever the driver presses the button to auto aim.

Closes #501

[JLLeitschuh]

If I have grip on a roborio and running via deploy then this will start both pipelines which will create unexpected (and really hard to diagnose) issues.

[ThomasJClark]

It'll only start both of them if they're both connected to the same NetworkTables server, which is probably a bad idea anyways

We could maybe make this only work on headless mode. I doubt anyone would need to use it in GUI mode

[codecov-io]

Current coverage is 49.78%

Merging #505 into master will decrease coverage by -0.50% as of f8f8d26

@@            master    #505   diff @@
======================================
  Files          130     131     +1
  Stmts         3884    3903    +19
  Branches       428     433     +5
  Methods          0       0       
======================================
- Hit           1953    1943    -10
+ Partial        110     108     -2
- Missed        1821    1852    +31

Review entire Coverage Diff as of f8f8d26

---

Uncovered Suggestions

1. +0.54% via .../ExceptionAlert.java#83...103
2. +0.38% via ...cketPreviewView.java#88...102
3. +0.38% via ...indowController.java#219...233
4. See 7 more...

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[JLLeitschuh]

This needs to work with the new --headless parameter.