Refactoring nrpe module (round 2/??)

/usr/local/lib/nagios/plugins directory for plugins shipped by module
Merge nrpe::packages and nrpe::service classes in nrpe class
nrpe class now accepts an allowed_hosts argument. It defaults to undef.
Cleaned-up Service['nagios-nrpe-server']
 hasrestart defaults to true in puppet 2.7
 hasstatus defaults to true in puppet 2.7 so pattern is not needed
 restart not needed (init script works fine)
Updated rspec examples
Updated puppet tests
Removed spec fixtures that caused a problem with puppet doc(cyclic deps)
Added Rake code to create and purge above fixtures before each run
Updated nrpe_local.cfg.erb
nrpe::check now ships virtual resources which are realized by nrpe class
virtual monitor_service resources tagged nrpe are no longer realized by
nrpe class (none existed anyway)

Change-Id: I96bcccae226c0b308ec528a52259d4c1bf764afb