support relative paths for data set linkouts (URL in annots.xml) for QuickLoad

This feature relates to mirroring IGB QuickLoad.

The annots.xml file tag has attribute "url"

When a data set (file) is displayed in the Available Data treeview, the URL is used to create the hyperlinked 'i' info icon linkout.

Feature request is:

If the url is relative (e.g., looks like foo/bar/baz.html or ./foo/bar/baz.html or /foo/bar/baz.html – anything lacking a protocol prefix such as http://, ftp://, or file://) then IGB should append the relative url path to the QuickLoad URL.

In other words, if it would be a valid link in a Web page, then it should work as an info hyperlink, and the web root should be the address of the QuickLoad site.

For example, if "url" attribute is "M_musculus_Dec_2011" and the server URL is "http://www.igbquickload.org/quickload", then the linkout from the info icon should be "http://www.igbquickload.org/quickload/M_musculus_Dec_2011"

Note that IGB will need to be able to handle url attributes that begin (or don't begin) with a leading slash and also that this will need to be tested with local quickload as well.