enhance input sort with the modal which display the available fields
Fix #34 : main agg is now really removed
Add visual control for sort's field to show that empty value will cause a search error
Fix a bad choice of bootstrap component when context saved
Fix #46, #51, #53, that fixesand enhance aggreagtion control, add a link to official doc about aggregations.
Remove debug lines
Merge pull request #55 from ErwanPigneul/master

Aggregations enhancement and controls...