fix for max key length errors in InnoDB tables.

Reducing the length of the username field in the Table Users from varchar(256) to varchar(255) prevents MySQL error "Specified key was too long; max key length is 767 bytes" which is a stated prefix limititation for MySQL InnoDB tables. Relevant for utf8 character encodings.

web/src/main/webapp/WEB-INF/classes/setup/sql/create/create-db-mysql.sql

@@ -125,7 +125,7 @@ CREATE TABLE RegionsDes
 CREATE TABLE Users
   (
     id            int           not null,
-    username      varchar(256)  not null,
+    username      varchar(255)  not null,
     password      varchar(120)  not null,
     surname       varchar(32),
     name          varchar(32),