Fork of CKAN's built-in Statistics plugin modified for data.gov.au

• Remove private datasets from all statistics (except top users)
• Add summary page
• Add activity summary page
• Add organisation public/private dataset count page
• Add two config directives:
  • dga.recent_time_period = 60
  • dga.recent_page_limit = 50
• Recently Created Datasets and Recently Updated Datasets statistics show changes since now minus dga.recent_time_period up to the dga.recent_page_limit

• CKAN 2.5+