Passing-by-reference deprecated

Pass-by-reference has been deprecated as of PHP 5.3.x causing a notice. As of PHP 5.4.x pass-by-reference is being removed. Function definitions alone are enough to correctly pass the argument by reference.
Merge pull request #204 from m4ikel/patch-1

Passing-by-reference deprecated
'key' column value should get from the config variable
replace 'key' to config_item('rest_key_column')
Update Format.php

Added a way of formatting the JSON to include the numeric check, but only if the available PHP version supports it (IE v5.3.3 or higher).
init request/response/rest to suppress PHP warnings
Escape double quotes per RFC 4180

According to this RFC:

      7.  If double-quotes are used to enclose fields, then a double-quote
          appearing inside a field must be escaped by preceding it with
          another double quote.
Merge pull request #218 from moberemk/master

Added proper JSON numeric formatting
Merge pull request #228 from justinethier/master

When outputting CSV escape double quotes per RFC 4180
Merge pull request #216 from shiroamada/master

replace 'key' to config_item('rest_key_column')
Merge pull request #224 from joeauty/master

Suppress PHP warnings
Added automated jsonp support with validation based on the presence of
the 'callback' GET param;
Also works should:
* the requesting Content-Type is application/json instead of application/javascript;
* the format GET param is: json
* file extension: .json
Removed _format_jsonp which depends on file extension .jsonp or 'format' query param;