Modify user() method option names to be case insensitive

[gitbrent]

The user() method takes options with names like title, email, etc.

If a user doesn't utilize the correct case, the user method returns the current user's properties (the API treats it as if a null value was passed). This is both an unwanted design outcome and a potentially confusing response for users.

The option names should be made case insensitive to correct the issue.

sprLib.user({ title:'Bill Gates' }).then(...) // Returns Bill's user properties
sprLib.user({ Title:'Bill Gates' }).then(...) // Returns the current users properties

[gitbrent]

Nah, this will only encourage junk coding practices.

Better idea: warn about this situation!

Now checked in: Console warning about invalid option property names.

[gitbrent]

Same option prop checks added to site().groups() and site().users()