Add move constructor and move assignment to Image

Add a move constuctor and move assignement to the Image data structure.
Also, fix some documentation warnings and build errors due to a missing
<array> include.
Remove initialization list initialization for std::array

Remove the initialization list initialization of a std::array member
variable in the Image class. This part of C++11 is not supported yet in
VS2012.
Fold the channels into the size in the Image class

Since the number of channels is really part of the Image size, it is now
folded into the member variable m_size. Previosly, getSize returned a 2
element array that held width and height. Now getSize returns a 3 element
array (width, height, channels).