sd-bus: rename sd_bus_get_owner_id() → sd_bus_get_bus_id()

The ID returned really doesn't identify the owner, but the bus instance,
hence fix this misnaming.

Also, update "busctl status" to show the ID in its output.
sd-bus: add new sd_bus_get_address() for querying the current bus address

Also, update "busctl" to show this in its output.
sd-bus: make more connection properties readable
update TODO
sd-bus: add arrays of strings in the bloom filter

Let's do this right from the beginning, to prepare ground for udev
messages that most likely want to store list of strings (for device
tags) in messages, and filter on them.
sd-bus: if a NULL signatures is passed to sd_bus_message_skip(), make it skip a single element of any type
sd-bus: add support for matches against arrays of strings in messages
update TODO
coredump: rework compose_open_fds()

Use FOREACH_DIRENT() and FOREACH_LINE() macros instead of manual loops.

Don't clobber return parameters on failure.

Simplify some other things.
coredump: simplify a few things by allocating small fields on the stack rather than heap