fix data flash when panning, close #2082

Layers that get opacity should be HW-composited like supersurface,
otherwise it flickers when panning. Should in theory improve
performance as well.
avoid excessive tooltip show/hide with mouseenter/leave
throttle hover for less epileptic experience and better perf

Otherwise the sidebar flashes so fast that it makes no sense while
distracting the user and lagging due to heavy sidebar construction.
Merge pull request #2088 from mourner/master

Fix data flash when panning, close #2082
dry up code for CSS transforms
Merge pull request #2090 from mourner/transform

Dry up code for CSS transforms
Merge pull request #2089 from mourner/better-hover

Better hover experience
Update GitHub links
Update OSM.org links
Add imagery update step to RELEASING
Update translations
Update imagery
1.3.5
Minor en.json update that got missed
protect against relation loops, part 2. fixes #2096
Merge pull request #2097 from tyrasd/patch-self-referencing-relations

protect against relation loops, part 2.