GLMixer Code

Closing properly Video File, and adding mechanisms to force thread
termination.

Added the type of the source as first specific property.

Compiling the undo history in rendering manager only if
HISTORY_MANAGEMENT flag is enabled.

Disabling use of avcodec_close as it locks the program (not thread
safe?). TODO: find a more elegant way to clean the codec.

Modularization of compilation with Session manager, Tags manager,
history manager and logger. Useful for debugging and compiling release
without unfinished features.

Cleaner exit on recorder (close all and terminate threads before
offering saving options to user).

Preventing deadlocks in multithreaded source update (use timeout on
locking).

Memory management fixes (valgrind).
Lock mutex in multithreaded source (video file and Algo) changed to
tryLock to prevent deadlocks.