Fix #64: Status cycling uses all "done" states

You can define several "to do" and "done" states separated by "|":

#+TODO: TODO NEXT STARTED | DONE CANCELLED

See ':help vimorg-todo-metadata'. You can cycle forth and back through
the states using <S-Enter> or <S-Left> and <S-Right>. When going through
the states, all "done" states should be used and not only the first one.
Merge pull request #69 from hfs/status-cycle

Fix #64: Status cycling should use all "done" states