Modularize misc::install-server classes

Creating install-server module by splitting up misc::install-server in
respective classes. Created WMF role::install-server, added
documentation and tests. This could probably be even more restructured
by splitting some classes into their own modules.

Big changes apart from the restructuring
* Stop using openbsd-inetd and falling back to using atftpd
in standalone mode.
* /usr/local/sbin/update-repository gets purged
* Some files obtain owner, group (they were missing that)
* Ditched custom iptables exec and now using ferm

Change-Id: Ia656e592cd07975f8d2f9bb63899c32dd7d2bdfd