mu4e: add few more header-functions to mu4e-view
mu4e: clean up address completion
Merge pull request #525 from jyp/master

mu4e: Allow to do retagging using marks instead of message actions
mu4e: Make :show-target be the identity by default

- This is certainly a better default than crashing
- The user is likely to omit this function in a majority of cases.
take a stab at the documentation of mu4e-marks