Fix SearchForm initialization

The default data were not included properly: repeatable field were not
stored in an Array, so the appending were based on the String#<< method
which is clearly not the right behavior.

This commit fixed this and fixes the tests which wrongly specified
default fields as arrays.
Fix the SearchForm#submit method

This method checked that the @ref was provided, not the given parameter,
so provided a argument to this method was useless.
SearchForm: #set, #query and #ref now returns the search form

These method can now be inlined (`form.ref().query().submit`)
Merge branch 'feature/fix-search-form'