e_output: Add APIs for stream capture to mask canvas with image object.

e_output: Add APIs for stream capture to mask canvas with image object.

This patch introduces APIs for masking canvas with image object during
stream capture. Namely, these methods are:

Eina_Bool e_output_stream_capture_mask_image_file_set(file)
Eina_Bool e_output_stream_capture_mask_image_geometry_set(x, y, w, h)

Once the image file is given, image object will be created on top of
canvas whenever starting stream capture and will be destroyed whenever
finishing stream capture.
It can be canceled by setting null as file name.

Image object will be re-loadeded if the file name changes during stream
capture, and will be destroyed if null is given as file name.

Change-Id: Id12895e894588c3700aeca52dab1213f57fdc44e