Theme path error in Windows

[DarTar]

(reported by Victor on the community list)

It appears that when running under Windows, Wikka 1.2 is unable to build correct links to theme dependencies (such as stylesheet).

e.g.

<link rel="stylesheet" type="text/css" href="templates\light/css/light.css?89bd2" />
<link rel="stylesheet" type="text/css" href="templates\light/css/print.css" media="print" />

we need to patch the GetThemePath() method to generate correct URI regardless of the underlying OS.

[BrianKoontz]

(In [1477]) Replace backslashes with forward slashes in <link> tags. Refs #913.