Add version filter to GET/experimental/syscollector/packages API call

[mgmacias95]

Hello team,

This PR closes #339.

This is an example of how the filter works:

# curl -u foo:bar "localhost:55000/experimental/syscollector/packages?pretty&version=0.17-1ubuntu1"
{
   "error": 0,
   "data": {
      "items": [
         {
            "scan": {
               "id": 1066845738,
               "time": "2019/03/04 16:39:27"
            },
            "multiarch": "foreign",
            "vendor": "Ubuntu Developers <[email protected]>",
            "description": "tool to manage well known user directories",
            "size": 533,
            "section": "utils",
            "version": "0.17-1ubuntu1",
            "architecture": "amd64",
            "priority": "optional",
            "format": "deb",
            "name": "xdg-user-dirs",
            "agent_id": "000"
         }
      ],
      "totalItems": 1
   }
}

Best regards,
Marta