Added a listener to the tabs(Search by city and Draw area) - so when we switch on the Draw area - the Draw Control is enabled(the draw control was added in draw_on_map.js). The data_handler.js when constructing the request uses either the content from Search by city or gets array of polygon coordinates(as specified by the polygon which the user is supposed to draw).

Added custom error message when the user has opened the Draw area, hasnt drawn anything, and presses update map.
Added arrows to the main api categories so better UI when collapsing/decollapsing them.