#155 Add option to send "standard" caption response

[Shrimpkin]

Adds force_caption_response to minidlna.conf. Users can force the "standard" caption response regardless of client type.

This or a similar feature might cut down the "add subtitle support for..." requests.

I only briefly tested this as I embed my subtitles.

[Sérgio M. Basto]

this isn't a duplication of yours patch in https://sourceforge.net/p/minidlna/patches/149/ , I can't apply the two patches at same time , give me conflicts ...