-fixed a minor error in finish_frame() where the amount of assigned frames was increased 1 instead of decreased 1.
-mortition() now decreases general_info.jobs_in_queue by one if the job is done and it calls distrenjob_remove() to remove the job from the linked list database.
-frame_finder() now increases the amount of assigned_frames by 1 if a frame to render is found
-distrenjob_remove() now decreases the amount of general_info.jobs_in_queue by 1
-prepare_distrenjob() now initializes assigned_frames and completed_frames at 0