Log Message:
khard: update to 0.15.1.

v0.15.0: 2019-10-24
- Require either default_action or a subcommand in the future (add deprecation
  warning for now)
- add man page for the config file
- make all options in the config file optional except for the address book
  definitions
- allow lists of strings for editor an merge_editor config options
- add a CONTRIBUTING file on Github
- handle ABLABELs on most fields
- add formatted name to the yaml template
- show formatted name in contact details
- make it possible to sort by and display formatted name in linstings
- remove the khard-runner.py helper script
- validate the config file upon loading it
- internal code refactoring