Add "font color" and "italic" tags management

Issue :  #8 Open *.srt subtitle file;

- Allow import and export tags :
	<i>italique</i>
	<font color="#ff00ff">rouge</font>

- Ctrl + RightClick on text edit zone :
  Allow change format for each characters selected,
  display a context menu -> Italic
		  Underline
		  Change color

- Fixed bugs :
  Read UTF8 encoded files instead "ISO8859-15"
  New sub insertion when "Shift" key is clicked -> bad behavior


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