Foreman » Smart Proxy

fixes #1567 - Foreman-proxy ignores dhcpd.conf include directive

Adding functionality that can detect and parse included files in dhcpd.conf.
Supports same syntax as dhcpd.conf(5) manual page specifies on the include
statement:

include "filename";

The include statement is used to read in a named file, and
               process the contents of that file as though it were entered in
               place of the include statement.

This parsing currently requires (unlike isc-dhcpd) that the include statement
is on it's own line, preceded by optional whitespace.