Add wave form viewer

Issue : #6 Create the waveform; #7 Allow to navigate in the video

Decode the waveform
Save the wave form in ".wf" file
Display the wave form
Zoom in/out wave form with Ctrl+mouse wheel
Shift the wave form with Shift+mouse wheel
Navigate in the video by mouse click in the wave form

Get and install the qwt library to compile.
See : http://qwt.sourceforge.net/

Signed-off-by: juiice <decaen.julien@gmail.com>
Add subtitles edition and display

Issue : #10 Edit subtitle file;
	#11 Display subtitle text in the video screen;
	#12 Edit subtitle text in the video screen;

Insert new subtitle with start time at video position
and with 1 sec duration
Edit subtitle text when playing directly in the video area
Display subtitles text in the video area

Signed-off-by: juiice <decaen.julien@gmail.com>