magit-push-dwim: fix interactive form
magit-push-dwim: don't prepend refs/heads/ to remote branch
magit-push-dwim: cosmetics
magit-get-remote/branch: new function
README.md: demote some headings
bump copyright years
magit-read-stash: fix
magit-apply-{diff,hunk}-item: use --ignore-space-change

Close #1139.
Merge pull request #1144 from sergv/fix/magit-read-stash

use queried stash id in magit-read-stash
magit.texi: remove obsolete information
magit-push{,-dwim}: improve doc-string