l10n: de.po: translate 38 new messages

Translate 38 new messages came from git.pot update in fe05e19
(l10n: git.pot: v2.1.0 round 1 (38 new, 9 removed)).

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
po/TEAMS: add new members to German translation team

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Merge git://github.com/git-l10n/git-po

* git://github.com/git-l10n/git-po:
  po/TEAMS: add new members to German translation team
  l10n: de.po: translate 38 new messages
subtree: make "all" default target of Makefile

You should be able to run "make" in contrib/subtree with no
arguments and get the "all" target. This was broken by
8e2a5cc (contrib/subtree/Makefile: use GIT-VERSION-FILE,
2014-05-06), which put the rule for GIT-VERSION-FILE higher
in the file.

We can fix this by putting an empty "all::" target at the
top of the file. That fixes this instance and future-proofs
against it happening again.

Reported-by: Jack Nagel <jacknagel@gmail.com>