Format code and new features

- General: apply format and clean up rules to code.
- General: migrate mongo driver version and force it to 2.11.3
- General: validate that Sentilo works fine with MongoDB versions 2.2.x
  and 2.4.x
- General: migrate spring-data-mongodb to the last stable release
- Catalog: add marketclustererplus and OverlappingMarkerSpiderfier plugins
  to group POIs by proximity into public visualizer.
- Catalog: naming refactor to distinguish between alarm  and alert.
- Catalog: add the option to select a provider when register a
  external alarm.
- Scripts: fix bug in buildSentilo.sh script. The appassembler plugin
  command was invalid.
- API: add new service to manage alerts.