Night mode tweaks

Merges, misc tweaks, removal of vast majority of !important
declarations.
CSS tweaks

Misc optimizations, merging multiple declarations, use of shorthand
where possible, removal of some vendor prefixes
RES Notification z-index

Prevent the notifications modal from falling beneath the header
Remove webkit-specific CSS

Apparently obsolete extra margin for Chrome/Safari.
Remove superfluous sidebar padding (night mode)
Merge pull request #253 from gavin19/master

CSS tweaks/fixes/night mode