Reset search results upon emptying input

[Anna-Livia]

When using legislation.openfisca.fr 's searchbar :

0. I see the list of all parameter and variable in alphabetical order
1. I enter "salaire" in the searchbar and hit "find"
2. I see the list of parameter and variables containing "salaire"
3. I hit "back" or do a blank search
4. The search result still shows the list of parameters and variables containing "salaire"

I think we should see the list of all parameter and variable in alphabetical order in step 4

[MattiSG]

• [x] Add a cross button to empty the search field and do a search on the right handside of the input field.
• [x] Reset filters upon making an empty search.