Add remove_callback method to ConfigParser.
Add ConfigParserProperty.
Don't rewrite same value multiple times, pep8 and doc fixes.
Set __properties before calling link/link_deps The alternative would be to make a post_init method, like link that is called after property is constructed.
Fix config.read() to call callbacks on all changes.
Add name attr to ConfigParser, name kivy and app config instances as such, and add method for ConfigParserProperty to register properties that use named config.
Set a ConfigParser for ConfigParserProperty using either a named config,or a config object, don't use property value for it anymore.
Undo changes to the link/link_deps order.
Use schedule to register the new property with config, instead of re-ordering link/link_deps.
Merge branch 'master' of https://github.com/kivy/kivy into configparser
Use the exiting app configparser instance. Prevents another parser with name='app' being created when restarting.
Merge pull request #1937 from matham/configparser

Adds a ConfigParserProperty class