fixed a problem with missing parameters on the PHPDoc for `get_sales()`
fixed some missing parameters for `get_earnings()`
Fixed missing parameters in PHPDocs for `get_best_selling()`
forced floatval() parsing. was receiving warning in PHPStorm without it because of relying on adding 2 strings together. it's better to be explicit than letting the intepreter decide.
fixed a missing parameter for `__construct` and removed unnecessary @return's in the PHPDocs
Added a missing parameter for the `edd_increase_total_earnings` PHPDoc
added a missing parameter to the PHPDoc for `edd_decrease_total_earnings()`