Move CameraServer and WPILib headers into their own folder

The old headers were moved into folders because doing so avoids polluting
the system include directories.

Folder names were also normalized to lowercase.

wpilibc/src/main/native/include/frc/PIDSource.h

@@ -0,0 +1,37 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2008-2018 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+namespace frc {
+
+enum class PIDSourceType { kDisplacement, kRate };
+
+/**
+ * PIDSource interface is a generic sensor source for the PID class.
+ *
+ * All sensors that can be used with the PID class will implement the PIDSource
+ * that returns a standard value that will be used in the PID code.
+ */
+class PIDSource {
+ public:
+  /**
+   * Set which parameter you are using as a process control variable.
+   *
+   * @param pidSource An enum to select the parameter.
+   */
+  virtual void SetPIDSourceType(PIDSourceType pidSource);
+
+  virtual PIDSourceType GetPIDSourceType() const;
+
+  virtual double PIDGet() = 0;
+
+ protected:
+  PIDSourceType m_pidSource = PIDSourceType::kDisplacement;
+};
+
+}  // namespace frc