Added new module: common/caps.py. This is the Capabilities centre of IVLE. It provides a Role class which is a rich enumeration type for Roles. The Role class will replace what has previously been simple strings used for Roles within the program. It has comparison ability to see if a Role is greater than or equal to another. This module also provides a set of capability objects which roles can be checked against. dispatch/login: Rather than setting 'rolenm' string in session, now sets 'role', a Role object. common/db: _escape allows Role objects, which get converted into strings. So the DB now accepts Role objects as values (though we don't make use of this currently). www/apps/tos: svn:ignore