[views/primary] some inner sections should use the `limit` by default to avoid a denial of service (closes #2719110) Today, it is possible to call .related and get a huge unlimited database-dos-inducing resultset that will be nevertheless limited a bit further in pure python in the `autolimited` view. While we cannot completely avoid potential denial of services such as these we mitigate the problem with the default ui settings: if the inner vid is `autolimited`, then the relation result sets is computed using the user-defined limit. This change respects the semantics of the `autolimited` view and shouldn't break anything.

import ConfigParser
try:
    undo_actions = config.cfgfile_parser.get('MAIN', 'undo-support', False)
except ConfigParser.NoOptionError:
    pass # this conf. file was probably already migrated
else:
    config.global_set_option('undo-enabled', bool(undo_actions))