Add some missing documentation (man pages and configuration information):

- man/man1/xenstore-chmod.1
- man/man1/xenstore-ls.1
- man/man1/xenstore.1
- share/doc/xen/xen-command-line.markdown
- share/doc/xen/xl-disk-configuration.txt
- share/doc/xen/xl-network-configuration.markdown

(jnemeth)