CndWriter is not fully compliant

[dantleech]

The CND writer seems not to produce a valid CND output in the following situation:

• Dump the nt:unstructured node type with the CndWriter
• Reimport the output with the CndReader

Results in:

PARSER ERROR: Expected token [Symbol, '[']. Current token is [Identifier, 'jcr'] at line 5, column 13
      Buffer lookup: "jcr . operator . equal "

@dbu suggests that we also migrate to using the Doctirne token parser.