Shuffle directories and filenames to get rid of historic cruft and to better reflect contrib/production status

The lowest last id  client can get ever have is 1 (0 is special), so first event must be 2, otherwise event with id 1 may get lost (thx bodik@cesnet.cz)

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

 * Changed charset to utf8 (not mb4, to support older MySQLs) in sqldump
 * Ditched data from clients (no predefined clients for new installations) in sqldump
 * Identity is renamed to name everywhere ii code and db to be consistent with Idea terminology
 * Better exception handling in insertLastReceivedId