Show subtitles in the table

Add hidden column to order subtitles as they are read from file.
GUI update

Fix layout inside QSplitter.
Remove Stretch menu item and add Modify group instead.
Move subtitlesTable update into seprate slot.
Replace Offset QTimeEdit with QSpinBox

As QTimeEdit does not allow negative values.
Fix tab order.
Subtitles: add scale function
Rescale subtitles
Tweak time labels
Calculate Offset and Factor from A1-B1 -> A2-B2
Transfer time from subtitles table to selected time box.

Add radio button to next to each time box (A1, A2, B1, B2). When
clicking on any Start or Stop cell in the subtitlesTable, the time from
that cell will be xferred to the selected time box.