Unit search filter functionality

[jennifermtan]

Only show the filters when filter icon is tapped.

• [x] Add a filter icon in the search bar from Google Fonts because it is imported already :)
• [x] Only display the filters pop up when the filter icon is clicked
• [x] Remove filters pop up it is tapped when visible AND on user input (if the user types something remove it because the units search pop up will appear as per #35)
• [x] Add a "clear all" button on the top right of the filters pop up
• [x] "Clear all" button will clear all selections

Currently:

Prototype: