Added 'init' module.
Added 'auth' module.
Added 'permissions' module.
Added 'users' module.
Added 'apps' module.
Initialization now offers response message on error.
Numerous changes. (See extended commit description)

API now responds over HTTP and HTTPS. (HTTPS is strongly reccomended).
Added HEAD and TRACE methods.
Changed DB engine from mysqli to PDO.
Added password hashing and checking methods.
Added 'is_authorized' method.
Changed default request method response from 200 OK. to 501 Not
Implemented. (request methods must be overridden by modules)