base support for custom ransackers
use ransackers as default filters
remove dashbord view

I think @seanlinsley forgot him in 86851c603c9627c54ef73f27cbef2e2ef18a30b5
Merge pull request #3562 from activeadmin/remove_dashboard_view

remove dashbord view
Merge pull request #3516 from activeadmin/base_filter_support_for_custom_ransackers

base support for custom ransackers
fix whitespace
inject URL parameter step
add new feature
Additional spec definition for preserving params on clearfilter.
Fixed errors.
refactor spec
add js to feature test
remove cgi
update param matching spec
remove unnecessary tests
implement feature
prevent test from loading a favicon