Fix Splark's name, change license to CC0

* Splark was misspelled as Splarc
* The original has been relicensed as CC0 - Public domain
Add "use dark theme" checkbox and default CSS for it

widescreen CSS still missing.

Also removes the dashed border on top of the "Frame Data" panel and moves "width: 260px" into the .framedata-sub class.
Add widescreen CSS for themes

also moves some declarations into the new CSS class "widescreen-separate".also moves some declarations into the new CSS class "widescreen-separate".also moves some declarations into the new CSS class "widescreen-separate".also moves some declarations into the new CSS class "widescreen-separate".
dos2unix two remaining files

charts/index.html and css/widescreen.css were still using DOS style line endings (CRLF).