Make search a first class citizen with ransack being the default engine (searchable fields)

[adrianthedev]

This would add the searchable option to fields.

We would build the search_query block ourselves.
If a field is deemed searchable we automatically add it to searchable_attributes on the model and add it to the search_query with _cont suffix. We might make a few adjustments, like marking the numeric DB columns as _eq instead.