Add form control for AND/OR
WIP on search controller changes to support AND/OR
Change continuous trait value to decimal instead of float
Add missing id and name to <select> element
Implement categorical search supporting AND/OR

Also: renamed trait_value_ids to trait_predicate for clarity
add comments about what the trait maps are
Populate search results completely so that template doesn't fetch values

WIP, and need to rewrite CSV template
Clean up output of trait values in results page
Refactoring to filtering on continuous trait values

Now supporitng AND/OR for continuous, and working
Need to see if categorical still works.
WIP
Finish refactoring to support AND/OR
Re-enable source references in search results html
Update results.csv template to comply with AND/OR refactoring
Merge pull request #36 from NESCent/trait_search_and_or

Implement AND/OR in trait search