Added Instagram square video option

[eduard-sukharev]

Also fixed having multiple video format options defined for hardsubbing and adjusting for Twitter/Instagram

This incorporates #1

I've moved out the composition of -vf parameter so that cmd line have only one -vf. This allows hardcoding subs and converting to suitable format in one go. Also, moved hardsubbing lower in order not to crop words when cropping video to 1:1 square format.