Generic Pointing Device (#1767)

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+## Pointing Device
+
+Pointing Device is a generic name for a feature intended to be generic: moving the system pointer arround.  There are certainly other options for it - like mousekeys - but this aims to be easily modifiable and lightweight.  You can implement custom keys to control functionality, or you can gather information from other peripherals and insert it directly here - let QMK handle the processing for you.
+
+To enable Pointing Device, uncomment the following line in your rules.mk:
+
+```
+POINTING_DEVICE_ENABLE = yes
+```
+
+To manipulate the mouse report, you can use the following functions:
+
+* `pointing_device_get_report()` - Returns the current report_mouse_t that represents the information sent to the host computer
+* `pointing_device_set_report(report_mouse_t newMouseReport)` - Overrides and saves the report_mouse_t to be sent to the host computer
+
+Keep in mind that a report_mouse_t (here "mouseReport") has the following properties:
+
+* `mouseReport.x` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing movement (+ to the right, - to the left) on the x axis.
+* `mouseReport.y` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing movement (+ upward, - downward) on the y axis.
+* `mouseReport.v` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing vertical scrolling (+ upward, - downward).
+* `mouseReport.h` - this is a signed int from -127 to 127 (not 128, this is defined in USB HID spec) representing horizontal scrolling (+ right, - left).
+* `mouseReport.buttons` - this is a uint8_t in which the last 5 bits are used.  These bits represent the mouse button state - bit 3 is mouse button 5, and bit 7 is mouse button 1.
+
+When the mouse report is sent, the x, y, v, and h values are set to 0 (this is done in "pointing_device_send()", which can be overridden to avoid this behavior).  This way, button states persist, but movement will only occur once.  For further customization, both `pointing_device_init` and `pointing_device_task` can be overridden.
+
+In the following example, a custom key is used to click the mouse and scroll 127 units vertically and horizontally, then undo all of that when released - because that's a totally useful function.  Listen, this is an example:
+
+```
+case MS_SPECIAL:
+        report_mouse_t currentReport = pointing_device_get_report();
+    if (record->event.pressed)
+    {
+        currentReport.v = 127;
+                currentReport.h = 127;
+                currentReport.buttons |= MOUSE_BTN1; //this is defined in report.h
+    }
+    else
+    {
+        currentReport.v = -127;
+        currentReport.h = -127;
+        currentReport.buttons &= ~MOUSE_BTN1;
+    }
+        pointing_device_set_report(currentReport);
+    break;
+```
+
+Recall that the mouse report is set to zero (except the buttons) whenever it is sent, so the scrolling would only occur once in each case.
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