Some misc CSS fixes and changes

* Removed the custom CSS thick-strikethough as can cause issues with wrapping and no longer really needed
* Re-added the original line-through
* Made tick sign on watched slightly more visible
* Reverted back to my original 'dimensions' for the poster view so that the new progress icons fit nicer(see note)
* Added a separate color for while a show is still adding
* Made the progress icons a fixed width & height so now the size doesn't change while the spinner is there

Note: With the poster dimensions, 163px seems to be the 'normal' size however some of them seem to be 169px and this causes the image to 'shrink' in height as CSS is making the image fit 'perfectly' in the div. I am currently unsure how to try and get around this and force the height, i'll keep looking into it.