[plugin report] Enhance the risk rendering system.

New:
    1. Automatically update the colors when loading the page.
    2. Inheritance of the colors:
        1. Local color for each plugin tab (max of the buttons).
        2. Local color for each test case (max of the tabs).
        3. Local color for each target (max of the test cases).

Change:
    1. Opacity changed from 0.5 to 0.7.
    2. Info risk is now green (succes) and Low risk is now light blue (info)
    because alert-* has no primary class.

Discussion:
    1. When test case's color comes from OWTF ranking value, the opacity might
    be to strong for the whole panel (might disturb the user).
    2. For a lot of test cases, might be too long to update each color (need
    some tests).