Merge branch 'filter-refs'

Merge branch 'filter-refs'

* filter-refs:
  Add links to the new refs page from summary page
  Add support for refs view
  Make cgit_print_branches()/cgit_print_tags() external
  Add descriptions of summary-branches and summary-tags to cgitrc
  Add support for config param summary-branches
  Move logic for age comparision from cmp_tag_age into cmp_age()
  Add support for config param summary-tags
  Sort tags by age
  Use reflist to print tag info
  Use reflist to print branch info
  Add functions and types for ref lists