Allow extra values as bool in options

 * "false", "off", "no", "-" are now allowed as false value
 * "true", "on", "yes", "+" are now allowed as true value

Author: boriel

src/api/options.py

@@ -96,7 +96,16 @@ def value(self, value):
         if value is not None and self.type is not None and not isinstance(value, self.type):
             try:
                 if isinstance(value, str) and self.type == bool:
-                    value = {'false': False, 'true': True}[value.lower()]
+                    value = {
+                        'false': False,
+                        'true': True,
+                        'off': False,
+                        'on': True,
+                        '-': False,
+                        '+': True,
+                        'no': False,
+                        'yes': True
+                    }[value.lower()]
                 else:
                     value = self.type(value)
             except TypeError: