Changed nargument names to valid identifers to avoid confusion

Argument names with whitespace like "jQuery object" are confusing,
because it might easily be mistaken for two arguments when reading the
signature. Argument names like "-index" are also confusing since they
look like an expression rather than a name. I have renamed the argument
names to be valid javascript identifiers, just like actual argument
names have to be. Also changed argument type "Object" and "PlainObject"
to "JQuery" where the prose documentation indicates that the type is a
jQuery object.
Changed argument name 'jQueryObject' to 'selection'

As per discussion on #jquery-content. Also changed type from 'Object'
to 'jQuery' where prose indicates a jQuery object.