[#33426] User profiles extending limited

In #__user_profiles table `profile_value` has been defined as varchar(255). This makes it quite limited for many custom fields which could be added to it, like various user descriptions. With this change the field is altered to text type instead, to enable storing of longer values.

No impact on the current entries. To test, enable user profile plugin, insert a few custom values, save, apply sql, make sure nothing changed, then apply some more changes to the profile.

Tracker: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33426&start=0