clarify getCurrentViewport

currentViewport was used as a shadowing local variable - this change is purely for code clarification.
GPU optim # 1

store uniform locations even if location returns -1. If uniform location would not be stored, many unnecessary glGetUniformLocation requests would be issued on every draw call.

This is especially pronounced if custom shaders were used which do not define the built-in shader uniforms.

Since the uniform locations cannot change once a shader is linked, a failure to look up the uniform on the first frame will also mean a failure to look it up on every following frame. By catching this early, we don't incur a driver overhead penalty per uniform per frame.
GPU optim #2

native viewport caching.

Since most apps just use one render viewport, it pays off to cache the render viewport and only issue a glGetInteger Query should the viewport have changed.

Before this, the viewport would have been queried twice a frame at least.

glGetInteger() has the potential for high driver overhead, since worst case the pipeline needs to be flushed before the query can return, and the CPU can continue issueing commands.
Update ofShader.cpp to use logging modules

There were a number of logging messages produced by ofShader that did not have the module set to "ofShader". This update fixes most of these. However, due to limitations in the ofLog interface there is no easy way to add module information to the ofLog messages that take a log level as an argument in the checkShaderInfoLog() function. To do so would need a constructor for ofLog that takes a module string as an argument or some other mechanism for providing module information.
Merge pull request #3472 from hardmanko/patch-1

Update ofShader.cpp to use logging modules
removes logic for internal cache of native viewport as @arturoc suggested.
+ simplifies things!
Merge pull request #3469 from HalfdanJ/documentation-math

Documentation math
Remove internal use of deprecated methods.
Merge pull request #3475 from bakercp/deprecation-fix

Remove internal use of deprecated methods.
Remove internal use of deprecated methods.
Merge pull request #3476 from bakercp/deprecation-fix

Remove internal use of deprecated methods.
ofGst: Fix compilation with GStreamer 0.10

I'm guessing GStreamer 1.0 is used these days, but I still have 0.10 on
a slightly old Fedora.
Merge pull request #3480 from dlespiau/20141213-gst-0.10-build-fix

ofGst: Fix compilation with GStreamer 0.10
ofGraphics Documentation and rearrangement
ofImage documentation
ofPath documentation
ofPixels documentation
Merge pull request #3283 from tgfrerer/feature-gpu-optimisations

Feature gpu optimisations
Polyline and pixels Documentation
ofTesselator documentation