Adding the support for the two other OpenCV linear filters to smooth
images. The new API does support spatial sigma in the bilateral filter,
hence bringing that property back.
Adding reference to new documentation.
The OpenCV cvSmooth function is deprecated [0] and the documentation
recommends to use GaussianBlur (). This makes the spatial property go
unused. Marking it as deprecated, making it non-functional and will remove
in the next cycle.
[0] http://docs.opencv.org/2.4/modules/imgproc/doc/filtering.html
The opencv element includes were full of duplicates and uneeded headers.
For example a few elements that stopped using gstcvopencvutils still
included that header file.
Change the file extension to cpp and add it into Makefile for consistency
with other elements of opencv and because Opencv not support C language in
new API 2.4.11.
https://bugzilla.gnome.org/show_bug.cgi?id=754148
