.jshintrc

config: document the purpose of the `format` config section

The config section now have a top level documentation to clarify its intend and
usage. In particular, user are now explain when the option are taken in account
and how to convert repository.

There are an handful of experimental options in this section that does not match
its definition. They should be relocated to other section before getting out of
experimental. (see next changeset for one example).

{
    // Enforcing
    "eqeqeq"        : true,     // true: Require triple equals (===) for comparison
    "forin"         : true,     // true: Require filtering for..in loops with obj.hasOwnProperty()
    "freeze"        : true,     // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
    "nonbsp"        : true,     // true: Prohibit "non-breaking whitespace" characters.
    "undef"         : true,     // true: Require all non-global variables to be declared (prevents global leaks)

    // Environments
    "browser"       : true      // Web Browser (window, document, etc)
}