Fix indent and whitespaces
Fix #3298 and few other fixes:

. Check for fixed array keys (pkg_categories_min_count,
  pkg_categories_max_display and pkg_default_categories) instead of
  undeclared variables
. Add a new default category "All"
. Use proper class on 'Category' columns when it is visible
. Increase Description column size instead of Name when Category is not
  visible
. Fix php short tags