Moved C++ comments from source files to headers (#1111)

Also sorted functions in C++ sources to match order in related headers.

wpilibc/src/main/native/include/DigitalOutput.h

@@ -23,16 +23,98 @@ namespace frc {
  */
 class DigitalOutput : public ErrorBase, public SendableBase {
  public:
+  /**
+   * Create an instance of a digital output.
+   *
+   * Create a digital output given a channel.
+   *
+   * @param channel The digital channel 0-9 are on-board, 10-25 are on the MXP
+   *                port
+   */
   explicit DigitalOutput(int channel);
+
   ~DigitalOutput() override;
+
+  /**
+   * Set the value of a digital output.
+   *
+   * Set the value of a digital output to either one (true) or zero (false).
+   *
+   * @param value 1 (true) for high, 0 (false) for disabled
+   */
   void Set(bool value);
+
+  /**
+   * Gets the value being output from the Digital Output.
+   *
+   * @return the state of the digital output.
+   */
   bool Get() const;
+
+  /**
+   * @return The GPIO channel number that this object represents.
+   */
   int GetChannel() const;
+
+  /**
+   * Output a single pulse on the digital output line.
+   *
+   * Send a single pulse on the digital output line where the pulse duration is
+   * specified in seconds. Maximum pulse length is 0.0016 seconds.
+   *
+   * @param length The pulse length in seconds
+   */
   void Pulse(double length);
+
+  /**
+   * Determine if the pulse is still going.
+   *
+   * Determine if a previously started pulse is still going.
+   */
   bool IsPulsing() const;
+
+  /**
+   * Change the PWM frequency of the PWM output on a Digital Output line.
+   *
+   * The valid range is from 0.6 Hz to 19 kHz.  The frequency resolution is
+   * logarithmic.
+   *
+   * There is only one PWM frequency for all digital channels.
+   *
+   * @param rate The frequency to output all digital output PWM signals.
+   */
   void SetPWMRate(double rate);
+
+  /**
+   * Enable a PWM Output on this line.
+   *
+   * Allocate one of the 6 DO PWM generator resources from this module.
+   *
+   * Supply the initial duty-cycle to output so as to avoid a glitch when first
+   * starting.
+   *
+   * The resolution of the duty cycle is 8-bit for low frequencies (1kHz or
+   * less) but is reduced the higher the frequency of the PWM signal is.
+   *
+   * @param initialDutyCycle The duty-cycle to start generating. [0..1]
+   */
   void EnablePWM(double initialDutyCycle);
+
+  /**
+   * Change this line from a PWM output back to a static Digital Output line.
+   *
+   * Free up one of the 6 DO PWM generator resources that were in use.
+   */
   void DisablePWM();
+
+  /**
+   * Change the duty-cycle that is being generated on the line.
+   *
+   * The resolution of the duty cycle is 8-bit for low frequencies (1kHz or
+   * less) but is reduced the higher the frequency of the PWM signal is.
+   *
+   * @param dutyCycle The duty-cycle to change to. [0..1]
+   */
   void UpdateDutyCycle(double dutyCycle);
 
   void InitSendable(SendableBuilder& builder) override;