[ie8] Fix lazy CSS loading and missing borders in search dropdown

- IE8 doesn't apply stylesheets added with jQuery. http://stackoverflow.com/a/6079832
It causes e.g. invisible search dropdown  https://github.com/owncloud/core/issues/3716#issuecomment-20197304
- Added border to the search results in IE as it doesn't support box-shadow.

cc @DeepDiver1975 @jancborchardt