fixing bug #4920
allowing to specify max length on 'textarea' field (except by UI)
defining constant String as parameter name and using it
by default, now 'textarea' field is higher and wilder...
Merge branch 'ney-bug4920' of git://github.com/NicolasEYSSERIC/Silverpeas-Core into NicolasEYSSERIC-ney-bug4920
Merge branch 'NicolasEYSSERIC-ney-bug4920' into core-5.13.x