Improve resizing experience slightly
improve alternate screenbuffer handling

Dont use a stack, but allways just allocate two screen_data. However,
make sure that the text objects are released when they are not in a
visible screen_data
If replace is on the first character of a style

and the previous style is compatible, then extend the previous style or
else the style list ends up with two compatible styles next to each
other
Make sure opacity level is reset when text is no longer blinking
Remove TerminalLine since its not used anymore