cbc: several minor changes (see description)

- Use 'expiry' everywhere instead of 'ttl'

- Allow to specify HTTP request body via stdin

- Don't make password mandatory for admin handles
  Some commands like flush don't need a password (or can use the
  bucket-level credentials)

- stats output should go to stdout, not stderr
  Makes it more easy to grep stuff

- support symlink invocation

Change-Id: I8987bfef7e949840816e034df3b9218098095295
Reviewed-on: http://review.couchbase.org/38686
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>