Clean up the CSS - Githubissues

In response to #477. PR opened so I can keep track of to-dos that crop up and weren't planned in the related issue.

[x] SCSS is better than CSS because it supports variables and nesting; use it
[x] Start using variables for shared colors of the palette; where necessary for layouts break these down into sub-divided variables that in the default layout refer to one single Standard Color
[x] Likewise break font sizes and so on down into variables
[x] Use em for font sizes? Also use relative font sizes in @media queries
[ ] Use CSS instead of manually modifying the HTML for the paginators
[x] The "no icon" thing in the header should display with the same formatting as if you have an icon (there are slight differences at present)
[x] The header should display identically between Firefox and Chrome if possible
[ ] Links in the nav-bottom header are hard to read on default layout
[x] Apply more the principle "style by what it is, not where it is"
[ ] Combine th and head if possible?
[ ] Get rid of the magic numbers still left in replies.scss
[x] Make sure the relevant of th, sub and subber work properly on the various layouts
[x] Separate subber and the thing at the end of form-tables (since they use different colors in some layouts and are semantically distinct)
[ ] Comb for manual padding that could be put into style rules (done .content-header, .post-subheader)
[x] Make sure the relevant header classes are used only where relevant; create new classes if necessary for other locations

glowfic-constellation / glowfic