Modify icon.

git-svn-id: http://svn.code.sf.net/p/openmediavault/code/trunk@1220 3c3d7b80-5828-415e-9f61-280b98178fff
Use SVG icon instead of PNG.

git-svn-id: http://svn.code.sf.net/p/openmediavault/code/trunk@1221 3c3d7b80-5828-415e-9f61-280b98178fff