GLMixer Code

Implementation of dialog to seek in a video by giving time or frame.
This involved cleaning up dialogs in glmixer and time computation
functions in VideoFile.

Compilation Fixed: issue with add_definition and set CMAKE_CXX_FLAGS.

Bug fix: Respect Fixed Aspect Ratio when changing scale in property
browser.

Cleanup Compilation of optional features and standardized #define
process. Make QtCreator happy by not using cmake add_definition (not
supported).

BugFix: cleanup mess with detection of end of video.

Added DISABLED status to Undo Manager

Work in progress - development of UNDO

Updated README.txt

compilation fix

Change computation methods for duration and framerate of video file.