Let some commands work with detached HEAD

add, resolved, and status didn't use the crt_series that was
initialized for them. So don't initialize it, since that means (1)
less work and (2) they won't fail when HEAD is detached.

Note that this doesn't completely fix the problem with detached HEAD:
a number of other commands (e.g. branch) don't always need to refer to
a current series, but currently fails on a detached HEAD even in those
situations.

Signed-off-by: Karl Hasselström <kha@treskal.com>