Restructure the unix agent scripts directory

At the moment the documentation recommends to put all the needed unix agent scripts into the directory /usr/lib/observium_agent/local.

This is very convenient but leads to the problem that the update of the scripts is not very easy/fast.

I would recommend the following set-up:

1) Save all scripts in the directory /usr/lib/observium_agent/plugins-available

2)Create in the directory }}{{/usr/lib/observium_agent/plugins-enabled symlinks to all the plugins which I want to have enabled.{{}}

This would allow us to create one package with all the agent scripts in it and we can update it a lot easier on all machines.

Or are there already other ideas around how you want to make it easier to install/update all those scripts?