Fauxton: redesign _changes-UI

Implement copying to clipboard
Change the view

Closes COUCHDB-2206
Fauxton: add external ZeroClipboard Dependency
Fauxton: remove the hidden tabs

Closes #200
couchserver: also serve files with cachebuster, remove the GET-Param
Changes from review:

Fix button text trigger
Toggle button gray on click
Change padding
Changes: Some button class cleanup