Check for CREATE permission on target NS (issue #4).

Also cleaned up some variable names and locations, a bit of documentation, and simplified some slightly circuitous conditionals.

Corrected EOLs for a couple of files.

Release: 2013-05-17.
Merge branch 'master' of https://github.com/samwilson/dokuwiki-plugin-addnewpage

Conflicts:
	plugin.info.txt
	script.js
	syntax.php
Use jQuery prop() rather than attr().