LESS cleanup + Team icons fix

Two issues should be solved with this commit:

1. All the .less files, with the exception of shelve.less, have been thoroughly lessified where possible, and contents of todo.less have been merged into common, frontpage, and sidebar, for comments/posts/header, announcements, and sidebar styles, respectively. In addition, [mixins](https://github.com/Echohawkdown/loleventvods/blob/master/less/mixins.less) have been added to the less directory and integrated (so far only `.border-radius` and `.bg-pos` are in use).

2. I have updated the team spritesheet with larger icons scraped directly from lolesports or Leaguepedia to address [icons looking similar to one another](http://www.reddit.com/r/VoDsBETA/comments/1vwv61/testpost_for_team_icons/cewvu0f), so they should be easier to distinguish now. In addition, I removed the vertical spacing between team icons, so the spritesheet should be a little smaller and easier to load now.