Added allowempty setting to ISEMAIL validator.

Till Brehm

2016-01-29 a8ab61eeb0beac52d5a1e8c41d549df4ed87bf71

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ALTER TABLE  `sys_session` CHANGE  `session_id`  `session_id` VARCHAR( 64 ) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL;