Improve template support from plugins

[acaproni]

Actually it is possible to replicate a plugin by means of templates (#81). For example a plugin that get the status of the antenna i can be generated by the plugin i. In this case we will need to run one plugin for each replicated device. Te use case of this replication is the plugin that gets the same monitor points by equal devices.
In ALMA we can think of a plugin that gets the status of one antenna.

This ticket is to support a different use case that is when one plugin gets the status of more devices but need to produce an output that can be used by replicated DASU.
In ALMA this is the case of the plugin that gets the status bits from the utility modules of all the antennas. This plugin is not replicated but we want the output to be replicated so that it can be the input of a replicated DASUs.

Actually a plugin can simply produce output by following the replication pattern describe in #80 but as it could possibly change, we should provide the plugin with a proper API.