Update / Fix Documentation for CND Notation

I started to learn Jackrabbit / JCA, but there was a documentation bug that took me long to figure out.

This is related to the CND documentation under http://jackrabbit.apache.org/doc/nodetype/cnd.html

I could not import my namespace and NodeType definition, until i

a) created the namespace in my repository (it's obvious i need to do this, but i thought, the namespace declaration on top of the cnd file would do this)
b) i declare the namespace "nt" in addition to my own namespace. i could not import anything but an empty node type, until i did this

eg. not just:

—
<myns="http://www.mynamespace.com/myns">
—

i needed to declare:

—
<myns="http://www.mynamespace.com/myns">
<nt = 'http://www.jcp.org/jcr/nt/1.0'>
—

before anything works. otherwise i got a strange exception (could not parse node type definition at "["??)