Reviewers: shindig.remailer_gmail.com, zhoresh, jtarrio,
Description: Makes it possible to modify MutableContent (ie in a rewriter) by raw content in addition to DOM and String. Please review this at http://codereview.appspot.com/1044042/show Affected files:java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/MutableContent.java java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/MutableContentTest.java
