Added struct af_features to store image features (aka keypoints).
Added features class to manage af_features structs.
Added FAST feature detector frontend.
Added FAST feature detector CPU backend.
Added FAST feature detector CUDA backend.
Added FAST feature detector OpenCL backend.
Added handlers for array type in features class.
Fixed failing abs() call for int/unsigned types on CUDA backend of FAST.
Added test reader for image input with array output.
Added FAST unit tests.
Merge remote-tracking branch 'upstream/devel' into fast
Fixed FAST files to comply with new directory structure.
Fixed data filename on FAST unit test.
Updating test/data submodule
Merge pull request #175 from pentschev/fast

Added FAST feature detector for all backends.
Fixed wrong memory type allocation on OpenCL backend of FAST.
Merge pull request #177 from pentschev/fast_opencl_fix

Fixed wrong memory type allocation on OpenCL backend of FAST.
FAST will return (af_)features instead of (af_)features *
Merge pull request #179 from pentschev/fast_return_fix

FAST will return (af_)features instead of (af_)features *
Merge branch 'devel' into graphics

Conflicts:
	include/arrayfire.h