SVG support

[kylekatarnls]

Hi, I updated today the IconViewer plugin but .svg preview failed (the default icon disappears but the preview does not appear. I will inspect that.

[jpmschuler]

Confirmed for different SVGs from different sources (e.g. FontAwesome 5): all SVGs show this behaviour using PHPStorm 2017.2.4 and IconViewer 1.13

[davidsommer]

@ kylekatarnls this is a litle private project with no ambitions :-) If anyone likes to contribute then i will add the support.