Clean-up and refactor of current OCIO integration

- Cleaned up some files -- seems there were some wrongly resolved
  conflicts which resulted into duplicated code in space_image.py
  and some build configuration files.
- Store all color space related data (such as display device, view
  transform and so) as strings, so it could easily be ported to new
  OCIO configuration files and it'll be much more portable between
  different configurations.

  This required adding some look-ups to RNA associated with such
  settings, but it's indeed the only way to do this. If it'll be
  figured out such look-ups causes performance issues it's possible
  to optimize this further using hash. So far it's only few elements
  in list to be looked up.
- Added support of display device transformation from OCIO
  configuration files. Display device is setting per-window and
  different windows could have different display devices, so it's
  possible to have one blender window opened on sRGB monitor and
  another one on xyz projector.

  Display device is ignored when using ACES ODT Tonecurve view
  transform due to it's not an OCIO transformation. Probably it'll
  be possible to get rid of this tone curve soon (if it'll be
  proved useless or it'll be implemented as a part of OCIO LUT).
- Movie Cache now supports deleter functions for user keys, so
  such keys could have some allocated data which would be removed
  as soon as element in cache is being removed.
- Movie Cache now support callbacks to check whether current
  cache element could be removed from a cache due to it wouldn't
  be accessed anymore.
- Re-written cache stuff for display buffers of ImBuf. Now it's
  using Movie Cache which is global for all ImBufs.

  Probably it's not implemented in fastest way, would be investigated
  further and probably changed it performance wouldn't be good enough.

source/blender/compositor/operations/COM_ViewerBaseOperation.cpp

@@ -35,6 +35,7 @@ extern "C" {
 	#include "MEM_guardedalloc.h"
 	#include "IMB_imbuf.h"
 	#include "IMB_imbuf_types.h"
+	#include "IMB_colormanagement.h"
 }
 
 
@@ -72,7 +73,10 @@ void ViewerBaseOperation::initImage()
 		anImage->ok = IMA_OK_LOADED;
 	}
 
-	imb_freerectviewImBuf_all(ibuf);
+	/* viewer might have been change size, invalidate cached
+	 * display buffers so they'll be used with a proper size
+	 */
+	IMB_display_buffer_invalidate(ibuf);
 
 	/* now we combine the input with ibuf */
 	this->m_outputBuffer = ibuf->rect_float;
@@ -88,7 +92,7 @@ void ViewerBaseOperation:: updateImage(rcti *rect)
 void ViewerBaseOperation::deinitExecution()
 {
 	ImBuf *ibuf = BKE_image_acquire_ibuf(this->m_image, this->m_imageUser, &this->m_lock);
-	imb_freerectviewImBuf_all(ibuf);
+	IMB_display_buffer_invalidate(ibuf);
 	BKE_image_release_ibuf(this->m_image, this->m_lock);
 
 	this->m_outputBuffer = NULL;