New: added new invaid sub files
Fix: made ssa parsing more robust

By removing the name check on the first line
And aggregate the text columns as text line can sometime
contain coma
Fix: SubViewer parser when a sub item's text is empty
Fix: MicroDvd parser when file begins by some annotations

For instance, the first line could be "text/plain".
We should be able to skip to irrelevant first lines.
Cleanup: reorganized subtitles test files
Fix: Ssa parser failing on empty lines
Fix: trying to extract framerate from empty line in MicroDvd parser
New: updated nuget version from 1.3.4 to 1.3.5