This converts password_file and acl_file checks to act like a v5 plugin.

Merge branch 'feature/add-deny-option-for-acl' of git://github.com/BrandtHill/mosquitto into BrandtHill-feature/add-deny-option-for-acl

This was happening when the client automatically reconnected.

Closes #1846. Thanks to DSOFreak.

This allows setting of a bind address independently of the
`mosquitto_connect*()` call.

Closes #1837. Thanks to chegancasb.

This happens regardless of whether the `-d` argument is used when
running the broker.

Closes #1845. Thanks to habazut.

Closes #1842. Thanks to Wolfgang Petroschka.

For #1225.