Cleanup spring configuration for statistics

[abollini]

The spring configuration and the backend code for the statistics is a mess.

yearsDate should be not a static attribute AStatComponentService but an instance attribute of the StatsComponent.

At the same time the
topCountryLength
topContinentLength
topCityLength
topRelation
attribute should be moved from the statisticscomponentservice to the componentbean to be used also in the SOLR query and not only as filtering on the view.

We can introduce a StatisticsConfigurationService to track a general configuration shared across all the component or we can rely on abstract bean to simply the configuration sharing common values across all the components. In this way one can always decide to have separated configuration for specific needs