add destroySession method

C. Fahner <christiaanenzo@gmail.com>
rename session_start -> session_create
rename SessionManager::startSession -> createSession

C. Fahner <christiaanenzo@gmail.com>
update reference SessionManager::startSession -> createSession

C. Fahner <christiaanenzo@gmail.com>
add ApiCall session_destroy

C. Fahner <christiaanenzo@gmail.com>