[jjo,r=mew] add basenode to memcached
Add a interface the nrpe-external-master subordinate
rework basenode to use exec.d/*/charm-pre-install
[jjo,r=mew] rework basenode to use exec.d/*/charm-pre-install
Add in a nagios check when we have a relation with nrpe-external-master
Make the nrpe-external-master-relation-changed hook executable
We need to export the variables for them to be recognisable to cheetah --env
Ship the nagios plugin for checking memcache as well
We need python-memcache for the nagios check in nrpe-external-master
[mthaddon] support for pre-install hook structure, support for the nrpe-external-master charm

This adds support for pre-install hook structure, as supported in a number of other charms, which allows you to do things like set timezone, install custom apt repositories, etc.. It also adds support for the nrpe-external-master charm