* Fixed case for all _e, esc_attr_e and esc_html_e strings
* Fixed case for all _n_noop strings
* Fixed case for all _x strings
* Fixed case for all __, esc_html__ and esc_attr__ strings
* Fixed a few more strings
* Fixed strings in unit tests
* Fix PayPal Standard case.
* Save Order text
* Added comments to properties that don’t have any.
* Added comment to `get_chart_widgets`, `customers_vs_guests` since it
was `method function`
* Added missing `exit if accessed directly`
* Updated `get_main_chart` comment since it is wrong.
* fixed indentation - swapped spaces for tabs at start of line, swapped
tabs for spaces min-line for alignment
* removed instances of `@return void` and `@access public`
* improved readability
@see http://make.wordpress.org/core/handbook/coding-standards/php/