Custom buttons Mozilla add-on

This is an unofficial repo for the custom buttons add-on

Fixed to work with Firefox 51+ and Thunderbird 47.7+

Problem: nsIDOMParser breaks the new DOMParser contructor globally on all Firefox versions.

Code in content/custombuttons/cbbutton.js was changed from

   var dp = Components.classes["@mozilla.org/xmlextras/domparser;1"].createInstance(Components.interfaces.nsIDOMParser);
   var doc = dp.parseFromStream(instr, null, instr.available(), "application/xml");

to

   var bis = Components.classes['@mozilla.org/binaryinputstream;1'].createInstance(Components.interfaces.nsIBinaryInputStream);
   bis.setInputStream(instr);
   var templateStr = bis.readBytes(bis.available());
   var doc = (new DOMParser()).parseFromString(templateStr, "application/xml");

• content/custombuttons/cbbuttonimpl.js had all function names to start with 'this.'