Assorted tweaks to tropo for foundation

* use _skin-colors.scss from dw-free (shared with other site skins)
* remove unneeded CSS, especially per-page selectors. We can add them in
  later if needed, but most need adjusting to Foundation anyway, so just
  get rid of them and adjust when converting
  (But really, we'll probably find out we don't need them, and end up
  with a more consistent UI all over)
* assorted tweaks to clean up tropo stylesheets
@import foundation into tropo-$color.css

So that we can set per-skin colors on the foundation variables
Various tweaks

* don't require zurb/foundation, let's use the one in our repository
* fix colors
* cleanup css code that foundation can take care of for us
Remove lj_base(-app).css from the foundation pages
Fix menu colors in tropo
Tweak appearance of the site skin search form in foundation
Move menu back to the bottom in the source order

* position with position: absolute
* add back in spacing around the edges of elements (for large screens /
  desktop?)
Fix logged-in account links in tropo
Remove underline of menu items
Fix logo positioning