Error/Info messages are more coherent, password now required to remove user, etc.

Error messages are now more consistent, if an error occurs it will be
returned under the property ‘cenError’.

If Cenny.js has something to say (e.g. info on sign-in attempt), it
will be returned under the property ‘cenInfo’.

_____

.user.remove() now requires the user password (first parameter) before
removing the user. Callback has been moved to second parameter.

________

+ Many more improvements, less error messages, and fewer bugs.
Merge branch 'master' of https://github.com/loadfive/cenny.js

Conflicts:
	client/cenny.js
	server/cenny.php