* Introduced a new text_style_t

* Introduced a new text_style_t
* basic support for SSA formatted subs. (disable with --no-subsdec-formatted option)
* changes to freetype renderer to support the font color, size and alpha options of text_style_t (other options are possible, just not implemented yet. Full text_style_t support requires a more advanced renderer though. )
* changes to modules to support text_style_t instead of the old sub options.
* Some changes to subsdec to only iconv to UTF-8 if source is !UTF-8.

refs #82

not supported are style runs (styles on substrings).