Added combined X509MixMatchAuthenticator, which allows for logging in both clients with hostname cert and with client name cert

Fixed first client's access without id (IndexError: tuple index out of range) (thanks to Radko Krkos)

getEvents - id<=0 now resets server's notion of client's id to last N events (and starts sending there)

 * Server is now in line with Idea spec concerning client names - they are stored in db and compared lowercase
 * Fixed duplicity check when adding/modifying client
 * Secret is not secret anyway, simplify Client and logging code

* fixed missing 'dml' modifier in some queries

Server now limits max accepted event size. events.data changed to longtext to accomodate longer events