wtapi: specify format to WikiTrust API
Remove E4X notation

I was using this as a hack for HEREDOC, but this has been deprecated.
The last suggestion at StackOverflow worked:
http://stackoverflow.com/questions/805107/how-to-create-multiline-strings
Removed remaining E4X usage

There is a new backtick operator for ECMAscript 6, but it doesn't work
in FF20.