add a confirmation message when cache is cleared

[mxmkmarquette]

add a confirmation dialog when we hit either clear all, frontpage, page, object, transient that the cache have really been clear a admin notification in that case that state:

• All cache have been cleared
• Frontpage cache have been cleared
• Page cache have been cleared
• Object cache have been cleared
• Transient cache have been cleared

i think it's maybe a great addition so that way we are sure that thing have been done.