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
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
Merge branch 'master' into bugfix-ofGet/SetBackgroundColor
Merge branch 'feature-scrollwheel-support' of https://github.com/fakob/openFrameworks into feature-scroll

Conflicts:
	libs/openFrameworks/app/ofAppRunner.cpp
	libs/openFrameworks/events/ofEvents.h
scroll event to float
fixes for ofDrawGridPlane, ofDrawGrid

+ fixes issue where central axis would not be drawn when non-integer tick count specified
+ fixes ofDrawGrid API to specify stepSize and numberOfSteps rather than scale, tickNumber
+ ensures numberOfSteps be a positive integer
changelog update
nmerge thread error logger
ofShader: fix logging messages
scroll: add scroll to ofxGui and ofEasyCam.
ofBaseApp: scroll double -> float
Fixes #3317. Make sure that pictureSize and previewSize have same aspect ratio
Changelog entry for change to OFAndroidVideoGrabber to fix image stretching problem on some devices
Merge pull request #3318 from brinkmwj/fugfix-ofandroidvideograbber-stretching-artifacts

Bug fix for camera stretching artifacts on some Android devices
getTextureReference -> getTexture
*getTexture -> *getTexturePtr
uniformized API:

loadMovie -> load
loadImage -> load
saveImage -> save
initGrabber -> setup

old methods are deprecated except in the base classes and implementations
where it's dropped completely
Merge pull request #3320 from arturoc/refactor-API

uniformize API:
Merge pull request #3316 from tgfrerer/fix-ticks+drawGridPanes

fixes for ofDrawGridPlane, ofDrawGrid