added scrollwheel support for GLFW

implemented scroll events based on the already provided scroll_cb in
ofAppGLFWWindow.cpp
fixed inconsistent indentation
deleted subproject in devApps
getPixelsRef -> getPixels

getPixelsRef() is a confusing method name and most beginners keep
using getPixels missing the additional functionality in ofPixels.

this deprecates all getPixelsRef methods and converts all:

```cpp
unsigned char * getPixels();
```

into

```cpp
ofPixels & getPixels();
const ofPixels & getPixels();
```

we might even want to remove the non-const version since it doesn't
really make sense to modify the internal pixels.

also adds a cast operator to unsigned char* to ofPixels so we don't break
any code except for the implementations of ofBaseVideo that will need
to change getPîxelsRef -> getPixels and remove the old method returning
unsigned char*
examples: remove use of unsigned char * gePixels() for ofPixels & getPixels()
gl: fix GLES for new unssuported calls
Merge branch 'master' of github.com:openframeworks/openFrameworks
android: fix getPixelsRef -> getPixels
Merge branch 'master' into refactor-getPixelsRef
ofxOpenCv: getPixelsRef -> getPixels
ofxAndroid, Emscripten and Kinect: getPixelsRef -> getPixels
ofPixels: deprecate cast operator so old access as unsigned char* receives a warning
ofMesh: fix wrong access on load
ofFile: fix uninitialized vars on some constructors
Merge pull request #3313 from arturoc/refactor-getPixelsRef

getPixelsRef -> getPixels
android paths.default.make: SDK_ROOT not needed anymore
android paths.default.make: change example to ndk 10b
ofxCvColorImage -> unsigned char* to ofPixels
update CHANGELOG
fix ofGet/SetBackgroundColor, replaces #1401

ofSetBackgroundColor has never worked properly, this fixes it
ofGetBackground is deprecated for ofGetBackgroundColor
ofBgColor removed completely, this will break old code but was really wrong
ofbBgClear removed for ofGetBackgroundAuto

also renderers now have to implement:

	startRender
	endRender

and windows need to call it in display.

windows don't need to set anymore the vieport, clear the bg...
now the renderers do that instead, before the window had to ask
the renderer if it had to clear the background and with which
color which was mixing the responsabilities of both classes and where
that info was stored