Improve the Main Page of COVALI

[ZihengSun]

Main
After load data, user need to know click file name to select variables. It's not very clear. - a little dialog to indicate clicking the file name to select variables.
After change color, contry/location names sometimes desapear. - probably power outage
Projection box is covered by color bar when display window is smaller. - to be done
Some of projections are not working at all (using ASR testing).
Hard to find delete layer or data icon. -
Maybe text under top left icons. - move over the buttons, pop up some text labels

[ZihengSun]

The tooltips and collapse button are added.