cli: Add core dump info to core show settings.

Adds two pieces of information to the core show settings command
which are useful in the context of getting backtraces.

The first is to display whether or not Asterisk would generate
a core dump if it were to crash.

The second is to show the current running directory of Asterisk.

ASTERISK-29866 #close

Change-Id: Ic42c0a9ecc233381aad274d86c62808d1ebb4d83