Adding SVGDescElement automatically causes element tag to have "DESC" capitalized which makes it a mismatch when loading from saved file because listed as lowercase "desc" in whitelist.

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What steps will reproduce the problem?
1.  Add a description child element to an element such as rect.
2.  Save the svg.  The save works fine.
3.  Load the saved svg file back.  Notice that the description is not loaded 
correctly to a desc element but as a node value to the element itself.

What is the expected output? What do you see instead?
Should add a child desc element with the text as the node value.

In what browser did you experience this problem? (ALL)

In what version of SVG-edit does the problem occur? (Latest trunk)

Please provide any additional information below.
This is a case-sensitive issue.  I've added the "DESC" for now.  Even when 
adding the element with lower-case, it looks like the code is transforming tag 
name to upper-case.  Thanks for the help.

Original issue reported on code.google.com by mxi...@acumium.com on 6 Jul 2012 at 3:32