Added set_wikimapia_api_key() to make API keys available for all Wikimapia API calls in a session so you don’t have to keep specifying the wm_api_key argument each time
Breaking changes
wm_get_by_id() changed the main argument from x to ids. This is more intuitive, since the function accepts vectors of length > 1. It is also easier to debug the code now. Help section fixed accordingly