Remove Control z-index:2

[chunlampang]

Motivation

Since there are a z-index on the control container, we cannot override the the z-index for a specify control.

Design

Instead of setting z-index: 2 to the control. Create a container for the popup and marker, which place before the control container.

Mock-Up

There will be no parent z-index. Developer can override the z-index to control which component is on the top.
Plugin developer can choose the container in which their components are placed.