Make sure ID's in embedded svg's are unique

[TowardsDeath]

When twice embedding an icon with a gradient definition, the second icon isn't rendered, because the ID isn't unique in the document.

Solution:

1. In the SvgService, we should check if the svg contains any ID's, and replace them with something unique (either replacing it entirely, or adding a random suffix).
2. In the same SVG, we should check any references to that ID (e.g. fill="url(#gradient)" and update them.