Implement searching continuous values

Refactored input names
Add symbols to continuous trait values element
Fix bug where Safari removes the last trait row

change this.remove() to $(this).remove()
Add checkboxes to search form

only_rows_with_data and include_references
Implement only_rows_with_data
Search results view and controller now only share one ivar
Implemented source/reference display in search results
change class of source_popover