#233 added support for changing/removing category and setting new post_price
renamed function #233
fixed pricing bug for free content #233
#233 Improved coding style, documentation, and function names
Merge branch 'feature/233_change_or_remove_category_price' of github.com:laterpay/laterpay-wordpress-plugin into feature/233_change_or_remove_category_price

Conflicts:
	laterpay/library/laterpay/LaterPay/Helper/Pricing.php
added type-casting on saving the category_id on Metabox-Controller, fixed broken check on removing category default price to set the category with highest price #233
removed length-check to switch the tab to global default price if no category is selected #233
added "hide" to category-pricing-box when no category is selected #233
added check for removing all categories with pricing #233
added check for missing param category_ids in POST-Request #233
Merge pull request #243 from laterpay/feature/233_change_or_remove_category_price

#233 added support for changing/removing category and setting new post_p...