Fallback to msfilter property if background-size is not supported.

Function to test support was required. IE6-8 supports background-size: auto; but not other options such as cover so had to test for ability to handle that.
Correct path to roundel icon.
No need to have fully qualified URIs for roundel icon paths
Merge pull request #1020 from colmjude/bgsizeDetect

Fallback to msfilter property if background-size is not supported.