Fix for cache empty assets

`function assets` returns style and script tags even if I pass assets of only one type to it. With this commit it checks result of compilation and returns tag only if this result is not empty.
Fix for #154

Fix for #154 "Galleries: Thumbnails of images added from folder aren't displayed"
https://github.com/aheinze/cockpit/issues/105
Fix for #105 (2)

with previous commit thumbnails are displayed only when variable site2media is empty (for user in admin group for example). now it works in both cases.
Fix for #105 (3)

with "Fix for #105 (2)" commit only first import from folder works if site2media is not empty. now i sure thumbnails displayed in all cases)
ecmascript 5+6 shim added
Merge pull request #119 from kinolaev/patch-2

Fix for #105
Merge pull request #118 from kinolaev/patch-1

Fix for caching empty assets
angular + uikit updated
scss parser updated
$locals property added
Update tags.js

I have error "undefined is not a function" when I trying to add first tag. This commit fix this wrong behavior.
Merge pull request #124 from jmas/patch-1

Update tags.js
Fixes #121
moved view caching to lexy class
renderer refactored to service
Fixes #126
collection_populate_one api function added
cleanup
Lime updated + cleanup
more cleanup