Different ColumnDefinition for different platforms (#62)

* solution v1

* migration changes

* change test field + new migrations

* fix poms

ebean-test/src/test/resources/migrationtest/dbmigration/sqlserver17/1.0__initial.sql

@@ -68,6 +68,7 @@ create table migtest_e_basic (
   status2                       nvarchar(1) default 'N' not null,
   name                          nvarchar(127),
   description                   nvarchar(127),
+  description2                  nvarchar(227),
   some_date                     datetime2,
   old_boolean                   bit default 0 not null,
   old_boolean2                  bit,