Don't upload tags with empty values
improve railway presets

* add preset for funiculars
* add preset for narrow gauge railways
* add gauge field to some railway presets
* add "electrified" field to some railway presets
fix geocode result classifications

use nominatim's "class" property instead of "type" for result
classifications when "type" is "yes". Happens for "bridge"s,
"tunnel"s, etc.
Added preset for veterinary
Add rest area and service area presets

Fixes #2074
Don't let mouseover trigger during fade out
Correct arrow direction on drawn segment (fixes #2078)
Protect against relation loops (fixes #2072)
Suppress radial menu when clicking warning (fixes #2035)
Add area=yes when necessary

Example: highway=pedestrian areas.

Fixes #2069
Placate jshint
Ensure "New Relation..." is always available (fixes #2066)
Clock preset
Restore deleted nodes that are discovered to have extant parents

This bug has existed since 1.0!

Fixes #2085
Remove unused variable
Update name suggestions
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