space z-index label from slider
replaced several kde-theme graphic elements by SVG which renders better
when pixels are scaled up as necessary on high-DPI displays

used fallbacks for inclusion by img and css as described here:

http://css-tricks.com/svg-fallbacks/

css: multiple background trick (fails on Android 2.3 but we'd need a
handheld-css there)
img: onerror handler replacing src

static/widget/themes/kde/svg-templates.svg contains them all and should be
reused for other graphics

TODO noted that templates/catmaid/index.html generates x and y input
elements, this should be done by navigator.js similar to sliders
made the in-title-bar display of neuronname nicer, i.e. no background,
text in line with all other text in the bar, simpler DOM

TODO find a better place to display neuronname
Merge pull request #647 from acardona/svg-icons

SVG icons for prettier high-DPI display