Fix eq apply-to-all in preferences.

* slotLoadEffectChainInSlot was deleted, so the emit did nothing.  Create
  a function to fix that behavior.
* Don't instant-apply eq and quickeffect selections -- wait for the user to hit apply.
  (Otherwise, what's the point of an apply button?)

fixes lp:1404525
Fixed CoverArtCacheTest.loadCover, was broken because new default cover is bigger than 300 px
If the single-eq checkbox is checked, always keep all decks' prefs in sync
Remove incorrect call
LateNight: fix knob composed graphic
Merge branch 'master' of github.com:mixxxdj/mixxx
Tabs -> spaces.
Fix sign warnings.
Deere: Switch to px instead of pt to avoid cross-platform font size issues.
Merge pull request #437 from ywwg/eq-prefs

Fix eq apply-to-all in preferences.
Spinny updates

* Add separate bg and mask paths to spinny -- the cover art goes between them
* Use pixmaps instead of images for scalable drawing
* Update LateNight with SVG spinnies
Fix spinny antialiasing
Fix spinnies in other skins
Merge pull request #440 from ywwg/spinny-svg

Spinny updates
LateNight: Delete old spinny graphics
Use non-deprecated form to set GL widget format.
Make spinny default to fixed bg size.
Default spinny covers off
Fix signal quality update unnecessarily chewing CPU
replaced ControlObjectThread with ControlObjectSlave