Changes in api

Changes in api

- Api functions can define an HTTP method to use to call them. "405 Method Not Allowed" is returned on error
- Api function that modify data accepts only POST as method.
- A list of HTTP return code related exception is added
- Api functions throw HTTP exceptions instead of return false or die()
- api_call() catches HTTP exceptions and return error message with corret HTTP response code
- api_format_items() returns also item activities count (# of like/dislike etc)
- api/friendica/photos/list return more info about photos. xml format added.
- api/friendica/photo/detail return more info, links to all sizes, no data except if 'size' parameter is passed. xml format added.
- new api api/friendica/activity/<verb> and api/friendica/activity/un<verb> to add or remove like/dislike/attend status