[entity] add a new `cw_linkable_rql` method
* the new method returns the entities that are or may be related to the
current one by the relation passed as an argument.
Closes #3738011.
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))